A Comprehensive Guide to the "te" Form

The te form is without doubt one of the most used and important conjugations in Japanese grammar. Unfailingly, you will hear it used in just about every conversation. It is probably the single piece of grammar that lets you move from speaking in short, separate sentences to being able to express yourself fluidly in clauses.

Because the te form is essentially a conjunctive form of the verb or adjective, it has no intrinsic tense of its own. It only has two forms—affirmative and negative. The tense of the entire sentence is determined by the final verb. This distinction of affirmative and negative is better understood through an example.

With the grammar we have learnt thus far we can say:

I ate breakfast. I went to work.

In this case we would use the te form on the verb to eat to join the sentence and say, “I ate breakfast and then went to work”. Now either you ate and then went to work or didn’t eat and then went to work—there are only two options.

The Basics

Before we jump into the (many) different usages of the te form, let’s look at how you form it. Both verbs and adjectives have te forms. Let’s start with verbs.

Verbs

Affirmative

Conjugating to the affirmative te form is very easy once you know the standard simple past tense for each verb. All we need to do is replace the final syllable of the past tense like so:

Verbs with the standard past tense ending in た ⇒ て
Verbs with the standard past tense ending in だ ⇒ で

[Gr.] Verb	Dict.	Simple Past	te Form
[1] to go	行いく	行いった	行いって
[1] to read	読よむ	読よんだ	読よんで
[2] to leave	出でる	出でた	出でて
[3] to do	する	した	して
[3] to come	来くる	来きた	来きて

The verb “to go” is one exception within the Group 1 verbs in terms of its conjugation.

Negative

There are two forms of the negative for verbs—the appropriate form depending on the usage. Generally, naide is used for negative requests (“please don’t…”) or doing something without doing another action, while nakute is used to express reasons (“because I didn’t…”) or to link negative states.

Naide (ないで)

We take the standard negative form and add で at the end.

[Gr.] Verb	Dict.	Neg.	Naide
[1] to go	行いく	行いかない	行いかないで
[1] to read	読よむ	読よまない	読よまないで
[2] to leave	出でる	出でない	出でないで
[3] to do	する	しない	しないで
[3] to come	来くる	来こない	来こないで

Nakute (なくて)

We take the negative form of the verb and replace the い with くて.

[Gr.] Verb	Dict.	Neg.	Nakute
[1] to go	行いく	行いかない	行いかなくて
[1] to read	読よむ	読よまない	読よまなくて
[2] to leave	出でる	出でない	出でなくて
[3] to do	する	しない	しなくて
[3] to come	来くる	来こない	来こなくて

Adjectives

Affirmative

For i-adjectives we change the い into a くて. For na-adjectives we add で (the te form of the auxiliary verb).

Adj.	Dict.	Te Form
Cheap	安やすい	安やすくて
Famous	有名ゆうめい	有名ゆうめいで

Negative

For i-adjectives we take the negative form and change the ない into なくて. For na-adjectives we change to the negative form of the auxiliary verb.

Adj.	Neg.	Te Form
Cheap	安やすくない	安やすくなくて
Famous	有名ゆうめいではない	有名ゆうめいではなくて

Note that for the na-adjective we are just using the なくて form of the auxiliary verb.

As mentioned above, the te form has many different usages but the main ones are as follows:

Creating a simple command for someone to do something.
Creating a simple conjunction (“I did A and then did B”).
Forming the present participle (“I am eating a cake”).
Expressing a means or a reason (“I argued with my friend and now we’re not speaking to each other”).
Asking permission to do something (“May I sit here?”).
Prohibition (“You must not”).

1. A Simple Command

On its own, the te form creates a request or order for someone else to do something.

映画館えいがかんに行いって。

Go to the cinema.

日本語にほんごを勉強べんきょうして。

Study Japanese.

However, the te form used in this way is a little direct in the wrong setting, and would typically be used among friends, towards children, or from a boss to his/her subordinates. It can, however, be “softened” considerably with the addition of ね.

しっかり勉強べんきょうしてね。

Study properly (“Make sure you study properly, okay?”)

It is more polite to use the te form with “please”.

薬くすりを飲のんでください。

Please take the medicine.

Note: In Japanese, you “drink” medicine.

仕事しごとをしてください。

Please do your work.

In fact, ください is an archaic conjugation of the honorific verb くださる which means “to deign”. Essentially, the phrase is asking the other person to deign to do something. It is used all the time and it is perfectly fine to remember it as a phrase that means “please do x”.

For the negative we need the ないで form.

このボタンを押おさないでください。

Please don’t press the button.

コンピューターで遊あそばないでください。

Please don’t play on the computer.

2. Using the te Form as a Simple Conjunction

One of the core functions of the te form is to express sequential order and join clauses, essentially creating the meaning of “and” in Japanese.

Verbs

Take the following as an example:

今日きょうは高校こうこうの友達ともだちと会あいました。新宿しんじゅくで一緒いっしょにランチしました。

Today I met a high school friend. We had lunch together in Shinjuku.

This would sound far better as two clauses rather than individual sentences. We can join them using the te form of the verb “to meet”.

今日きょうは高校こうこうの友達ともだちと会あって、新宿しんじゅくで一緒いっしょにランチしました。

Today I met a high school friend, and we had lunch together in Shinjuku.

Firstly, note that the te form also dictates the chronological order of events—first you met your friend, and then you had lunch. Secondly, note that the tense of the entire sentence is determined only by the final verb. In English, for each individual clause in the sentence we need to adjust the tense of the verb accordingly.

私わたしは仕事しごとに行いって、友達ともだちと食事しょくじをしました。

I went to work and then had dinner with a friend.

私わたしは仕事しごとに行いって、友達ともだちと食事しょくじをします。

I will go to work and then have dinner with a friend.

Nor are we limited to using the te form only once. Overuse, however, sounds just as unnatural in Japanese as it does in English.

今日きょうは起おきて、学校がっこうに行いって、授業じゅぎょうを受うけて、家いえに帰かえりました。

Today, I woke up, and then I went to school, and then I took a class, and then I went home.

Using the te form of the verb “to hold” with the verbs “to go” and “to come” we can create the verbs “to take” and “to bring”.

雨あめが降ふります。傘かさを持もって行いってください。

It will rain. Please take your umbrella.

ビールを持もってきました。

I brought beer.

For a negative sentence we must use the ないで form.

朝あさご飯はんを食たべないで会社かいしゃに来きました。

I came to work without eating breakfast.

宿題しょくだいを忘わすれないで学校がっこうに来きてください。

Please come to school without forgetting your homework.

Finally, let’s not forget about the auxiliary verb because that helps us join clauses ending in nouns.

沙織さおりは新あたらしい会社員かいしゃいんで、明日あしたから働はたらきます。

Saori is a new employee of the company and will work from tomorrow.

和田わださんは先生せんせいじゃなくて、学生がくせいですよ。

Wada-san isn’t a teacher—he’s a student.

Remember that we can change では to じゃ.

Adjectives

The te form with adjectives lets us turn…

彼女かのじょはきれいです。彼女かのじょはやさしいです。

She is pretty. She is kind.

… into…

彼女かのじょはきれいで、やさしいです。

She is pretty and kind.

和田わださんは体からだが大おおきくて、顔かおが丸まるいです。

Wada-san is large with a round face.

3. Forming the Present Participle

So far we’re able to say, “I eat”, “I won’t eat”, “I ate”, and “I didn’t eat” but we can’t yet express the current state of “eating”. In fact, we’ve already learned it—we just need to combine the te form of the verb with the verb “to exist”!

勉強べんきょうしている。

I’m studying.

I study and then I exist… so I’m studying! We already know the conjugation for the verb いる (group 2) and so saying “I am not studying”, “I was studying” and “I wasn’t studying” is easy.

今いま、全然ぜんぜん運動うんどうしていません。

I’m not exercising at all at the moment.

まだレポートを提出ていしゅつしていない。

I’ve not yet submitted the report.

You will see the combination of まだ and the negative present participle often. まだ means “yet” and is used with the negative present participle. The phrase is very likely to appear in the N5 JLPT examination.

彼女かのじょはまだ着ついていません。

She’s not arrived yet.

最近さいきん、何なにをしていましたか。

What have you been doing recently?

4. Expressing A Means or a Reason

The te form can also be used to express a means or reason for a subsequent action or event.

Verbs

With positive sentences the difference in grammatical usage between expressing sequential order and expressing a means or reason can be a little ambiguous.

朝寝坊あさねぼうして、会社かいしゃに遅刻ちこくしました。

I overslept and was late for work.

昨日きのう、酔よっ払ぱらって、財布さいふをなくしましたよ。

Yesterday, I got drunk and lost my wallet!

自転車じてんしゃに乗のって、仕事しごとに行いきました。

I rode my bicycle to work.

The difference becomes clearer with intransitive verbs.

電車でんしゃが遅おくれて、飛行機ひこうきに乗のれませんでした。

The train was delayed and so I couldn’t board my flight.

It is clear that we are expressing a reason when we use the negative as we must use the なくて form.

ごめんなさい！電波でんぱがなくて、電話でんわできませんでした。

Sorry! I didn’t have any signal so I couldn’t call.

飛行機ひこうきに間まに合あわなくて、旅行りょこうに行いけませんでした。

I didn’t make it on time for the plane and so I couldn’t go on holiday.

Two common “phrases” are to use the te form with よかった and すみません (this structure may come up in JLPT N4/N5) to express gladness or regret at an action.

電話でんわしてよかったです。

It’s a good job I called you.

会議かいぎに遅おくれてすみません。

Sorry I was late for the meeting.

Incidentally, when I introduced the で particle, I explained that one of its usages is to express a reason. It was in fact the te form of the auxiliary verb that was being used not the で particle—a technicality given that they are identical, but one which is worth noting.

Adjectives

There is no chronological sequence of actions for adjectives so in the below sentences it is clear the te form is being used to give a means or a reason.

仕事しごとが忙いそがしくて、ランチを食たべる時間じかんがありません。

I’m so busy with work I don’t have time to eat lunch.

裕輔ゆうすけは納豆なっとうが好すきで、よく食たべます。

Yusuke likes natto and so he often eats it.

靴くつが安やすくて、買かいました。

The shoes were cheap so I bought them.

It’s worth spending a minute thinking about the different meaning of the above example sentence and the following:

安やすい靴くつを買かいました。

I bought cheap shoes.

The latter sentence is factual and doesn’t tell us anything about why you bought the shoes; whereas the former sentence suggests that if the shoes had been expensive you might not have bought them.

図書館としょかんが静しずかで、好すきです。

I like the library because it’s quiet.

5. Even If / Asking Permission

Used with も the te form can create the expression “even if” (as in, “even if it is expensive I will buy it”). Take a look at these two sentences:

いっぱい食たべて、太ふとりません。

I will eat lots and not get fat.

いっぱい食たべても、太ふとりません。

Even if I eat lots, I will not get fat.

The simple introduction of も in the second sentence changes the meaning completely. Very often learners are introduced to this structure as a set phrase to ask permission to do something.

電話でんわしてもいいですか。

May I make a phone call?

Literally, you’re asking, “Even if I make a phone call, is that good?”

こちらでタバコを吸すっても大丈夫だいじょうぶですか。

Is it okay if I smoke here?

The two phrases below will almost certainly appear on the JLPT. Both mean, “Is it okay if I…?”

〜してもいいですか。

〜しても大丈夫だいじょうぶですか。

大丈夫だいじょうぶ might just be the most common word in the Japanese language. 大 means “big” and 丈夫 means “robust”, but together they create the most common way of saying, “Nothing wrong” or “No problem”.

For the auxiliary verb, the same phrase becomes でも: the te form of the auxiliary verb with the addition of も.

ビールはありません。お茶ちゃでも大丈夫だいじょうぶですか。

I don’t have any beer. Is green tea okay?

The same structure can also be used with the negative.

〜しなくてもいいですか。

〜しなくても大丈夫ですか。

電話番号でんわばんごうを書かかなくても大丈夫ですか。

Is it okay if I don’t write my telephone number?

The negative is a little confusing. Instinctively, you might expect to see も added to the ないで structure because this was the form required to join phrases or express sequential order, and the logic here is basically saying the same thing; namely, “even if I do not A, B will/will not happen”. However, we actually have to use the なくて form! Why? Because the negative verb ending ない conjugates exactly like an i-adjective. Just as 高い (expensive) becomes 高くても (even if it is expensive), 食べない (will not eat) becomes 食べなくても (even if I do not eat).

運動うんどうしなくても、太ふとらない。

Even if I don’t exercise, I will not get fat.

彼かれは頭あたまがいいです。勉強べんきょうしなくても、試験しけんに合格ごうかくします。

He’s clever. Even if he doesn’t study he will pass the exam.

And we can apply the same grammar to adjectives.

試験しけんが難むずかしくても頑張がんばります。

Even if the exam is difficult I will do my best.

このブランドの品質ひんしつが悪わるくて、安やすくてもぜったい買かわない。

The quality of this brand is poor so even if it’s cheap I definitely won’t buy it.

6. Prohibition (“You must not”)

Because we can use the te form to ask for permission, we can also use it to deny permission or state a strict rule. To say “you must not” do something, we combine the te form with はいけません (formal) or はだめです (casual).

ここで写真しゃしんを撮とってはいけません。

You must not take pictures here.

そのケーキを食たべてはだめですよ。

You must not eat that cake.

Note: In spoken Japanese, ては is very frequently contracted to ちゃ. Therefore, 食べてはだめ becomes 食べちゃだめ.

The いけません is, in fact, the negative potential form of the verb “to go”. In other words, the literal translation for this usage would be:

〜てはいけません。

As for doing this action, it cannot go.

In this respect, it might help to think of the English idiom “that won’t do”, which is about as close to a natural but direct translation as you can get.

Of course, いけません does not have to be in the polite form.

美術館の中で　写真を　撮ってはいけない。

You must not take pictures inside the art museum.

Grammar Guide

A Comprehensive Guide to the "te" Form

With the grammar we have learnt thus far we can say:

I ate breakfast. I went to work.

The Basics

Before we jump into the (many) different usages of the te form, let’s look at how you form it. Both verbs and adjectives have te forms. Let’s start with verbs.

Verbs

Affirmative

Conjugating to the affirmative te form is very easy once you know the standard simple past tense for each verb. All we need to do is replace the final syllable of the past tense like so:

Verbs with the standard past tense ending in た ⇒ て
Verbs with the standard past tense ending in だ ⇒ で

[Gr.] Verb	Dict.	Simple Past	te Form
[1] to go	行いく	行いった	行いって
[1] to read	読よむ	読よんだ	読よんで
[2] to leave	出でる	出でた	出でて
[3] to do	する	した	して
[3] to come	来くる	来きた	来きて

The verb “to go” is one exception within the Group 1 verbs in terms of its conjugation.

Negative

Naide (ないで)

We take the standard negative form and add で at the end.

[Gr.] Verb	Dict.	Neg.	Naide
[1] to go	行いく	行いかない	行いかないで
[1] to read	読よむ	読よまない	読よまないで
[2] to leave	出でる	出でない	出でないで
[3] to do	する	しない	しないで
[3] to come	来くる	来こない	来こないで

Nakute (なくて)

We take the negative form of the verb and replace the い with くて.

[Gr.] Verb	Dict.	Neg.	Nakute
[1] to go	行いく	行いかない	行いかなくて
[1] to read	読よむ	読よまない	読よまなくて
[2] to leave	出でる	出でない	出でなくて
[3] to do	する	しない	しなくて
[3] to come	来くる	来こない	来こなくて

Adjectives

Affirmative

For i-adjectives we change the い into a くて. For na-adjectives we add で (the te form of the auxiliary verb).

Adj.	Dict.	Te Form
Cheap	安やすい	安やすくて
Famous	有名ゆうめい	有名ゆうめいで

Negative

For i-adjectives we take the negative form and change the ない into なくて. For na-adjectives we change to the negative form of the auxiliary verb.

Adj.	Neg.	Te Form
Cheap	安やすくない	安やすくなくて
Famous	有名ゆうめいではない	有名ゆうめいではなくて

Note that for the na-adjective we are just using the なくて form of the auxiliary verb.

As mentioned above, the te form has many different usages but the main ones are as follows:

Creating a simple command for someone to do something.
Creating a simple conjunction (“I did A and then did B”).
Forming the present participle (“I am eating a cake”).
Expressing a means or a reason (“I argued with my friend and now we’re not speaking to each other”).
Asking permission to do something (“May I sit here?”).
Prohibition (“You must not”).

1. A Simple Command

On its own, the te form creates a request or order for someone else to do something.

映画館えいがかんに行いって。

Go to the cinema.

日本語にほんごを勉強べんきょうして。

Study Japanese.

しっかり勉強べんきょうしてね。

Study properly (“Make sure you study properly, okay?”)

It is more polite to use the te form with “please”.

薬くすりを飲のんでください。

Please take the medicine.

Note: In Japanese, you “drink” medicine.

仕事しごとをしてください。

Please do your work.

In fact, ください is an archaic conjugation of the honorific verb くださる which means “to deign”. Essentially, the phrase is asking the other person to deign to do something. It is used all the time and it is perfectly fine to remember it as a phrase that means “please do x”.

For the negative we need the ないで form.

このボタンを押おさないでください。

Please don’t press the button.

コンピューターで遊あそばないでください。

Please don’t play on the computer.

2. Using the te Form as a Simple Conjunction

One of the core functions of the te form is to express sequential order and join clauses, essentially creating the meaning of “and” in Japanese.

Verbs

Take the following as an example:

今日きょうは高校こうこうの友達ともだちと会あいました。新宿しんじゅくで一緒いっしょにランチしました。

Today I met a high school friend. We had lunch together in Shinjuku.

This would sound far better as two clauses rather than individual sentences. We can join them using the te form of the verb “to meet”.

今日きょうは高校こうこうの友達ともだちと会あって、新宿しんじゅくで一緒いっしょにランチしました。

Today I met a high school friend, and we had lunch together in Shinjuku.

私わたしは仕事しごとに行いって、友達ともだちと食事しょくじをしました。

I went to work and then had dinner with a friend.

私わたしは仕事しごとに行いって、友達ともだちと食事しょくじをします。

I will go to work and then have dinner with a friend.

Nor are we limited to using the te form only once. Overuse, however, sounds just as unnatural in Japanese as it does in English.

今日きょうは起おきて、学校がっこうに行いって、授業じゅぎょうを受うけて、家いえに帰かえりました。

Today, I woke up, and then I went to school, and then I took a class, and then I went home.

Using the te form of the verb “to hold” with the verbs “to go” and “to come” we can create the verbs “to take” and “to bring”.

雨あめが降ふります。傘かさを持もって行いってください。

It will rain. Please take your umbrella.

ビールを持もってきました。

I brought beer.

For a negative sentence we must use the ないで form.

朝あさご飯はんを食たべないで会社かいしゃに来きました。

I came to work without eating breakfast.

宿題しょくだいを忘わすれないで学校がっこうに来きてください。

Please come to school without forgetting your homework.

Finally, let’s not forget about the auxiliary verb because that helps us join clauses ending in nouns.

沙織さおりは新あたらしい会社員かいしゃいんで、明日あしたから働はたらきます。

Saori is a new employee of the company and will work from tomorrow.

和田わださんは先生せんせいじゃなくて、学生がくせいですよ。

Wada-san isn’t a teacher—he’s a student.

Remember that we can change では to じゃ.

Adjectives

The te form with adjectives lets us turn…

彼女かのじょはきれいです。彼女かのじょはやさしいです。

She is pretty. She is kind.

… into…

彼女かのじょはきれいで、やさしいです。

She is pretty and kind.

和田わださんは体からだが大おおきくて、顔かおが丸まるいです。

Wada-san is large with a round face.

3. Forming the Present Participle

勉強べんきょうしている。

I’m studying.

今いま、全然ぜんぜん運動うんどうしていません。

I’m not exercising at all at the moment.

まだレポートを提出ていしゅつしていない。

I’ve not yet submitted the report.

You will see the combination of まだ and the negative present participle often. まだ means “yet” and is used with the negative present participle. The phrase is very likely to appear in the N5 JLPT examination.

彼女かのじょはまだ着ついていません。

She’s not arrived yet.

最近さいきん、何なにをしていましたか。

What have you been doing recently?

4. Expressing A Means or a Reason

The te form can also be used to express a means or reason for a subsequent action or event.

Verbs

With positive sentences the difference in grammatical usage between expressing sequential order and expressing a means or reason can be a little ambiguous.

朝寝坊あさねぼうして、会社かいしゃに遅刻ちこくしました。

I overslept and was late for work.

昨日きのう、酔よっ払ぱらって、財布さいふをなくしましたよ。

Yesterday, I got drunk and lost my wallet!

自転車じてんしゃに乗のって、仕事しごとに行いきました。

I rode my bicycle to work.

The difference becomes clearer with intransitive verbs.

電車でんしゃが遅おくれて、飛行機ひこうきに乗のれませんでした。

The train was delayed and so I couldn’t board my flight.

It is clear that we are expressing a reason when we use the negative as we must use the なくて form.

ごめんなさい！電波でんぱがなくて、電話でんわできませんでした。

Sorry! I didn’t have any signal so I couldn’t call.

飛行機ひこうきに間まに合あわなくて、旅行りょこうに行いけませんでした。

I didn’t make it on time for the plane and so I couldn’t go on holiday.

Two common “phrases” are to use the te form with よかった and すみません (this structure may come up in JLPT N4/N5) to express gladness or regret at an action.

電話でんわしてよかったです。

It’s a good job I called you.

会議かいぎに遅おくれてすみません。

Sorry I was late for the meeting.

Adjectives

There is no chronological sequence of actions for adjectives so in the below sentences it is clear the te form is being used to give a means or a reason.

仕事しごとが忙いそがしくて、ランチを食たべる時間じかんがありません。

I’m so busy with work I don’t have time to eat lunch.

裕輔ゆうすけは納豆なっとうが好すきで、よく食たべます。

Yusuke likes natto and so he often eats it.

靴くつが安やすくて、買かいました。

The shoes were cheap so I bought them.

It’s worth spending a minute thinking about the different meaning of the above example sentence and the following:

安やすい靴くつを買かいました。

I bought cheap shoes.

The latter sentence is factual and doesn’t tell us anything about why you bought the shoes; whereas the former sentence suggests that if the shoes had been expensive you might not have bought them.

図書館としょかんが静しずかで、好すきです。

I like the library because it’s quiet.

5. Even If / Asking Permission

Used with も the te form can create the expression “even if” (as in, “even if it is expensive I will buy it”). Take a look at these two sentences:

いっぱい食たべて、太ふとりません。

I will eat lots and not get fat.

いっぱい食たべても、太ふとりません。

Even if I eat lots, I will not get fat.

The simple introduction of も in the second sentence changes the meaning completely. Very often learners are introduced to this structure as a set phrase to ask permission to do something.

電話でんわしてもいいですか。

May I make a phone call?

Literally, you’re asking, “Even if I make a phone call, is that good?”

こちらでタバコを吸すっても大丈夫だいじょうぶですか。

Is it okay if I smoke here?

The two phrases below will almost certainly appear on the JLPT. Both mean, “Is it okay if I…?”

〜してもいいですか。

〜しても大丈夫だいじょうぶですか。

大丈夫だいじょうぶ might just be the most common word in the Japanese language. 大 means “big” and 丈夫 means “robust”, but together they create the most common way of saying, “Nothing wrong” or “No problem”.

For the auxiliary verb, the same phrase becomes でも: the te form of the auxiliary verb with the addition of も.

ビールはありません。お茶ちゃでも大丈夫だいじょうぶですか。

I don’t have any beer. Is green tea okay?

The same structure can also be used with the negative.

〜しなくてもいいですか。

〜しなくても大丈夫ですか。

電話番号でんわばんごうを書かかなくても大丈夫ですか。

Is it okay if I don’t write my telephone number?

The negative is a little confusing. Instinctively, you might expect to see も added to the ないで structure because this was the form required to join phrases or express sequential order, and the logic here is basically saying the same thing; namely, “even if I do not A, B will/will not happen”. However, we actually have to use the なくて form! Why? Because the negative verb ending ない conjugates exactly like an i-adjective. Just as 高い (expensive) becomes 高くても (even if it is expensive), 食べない (will not eat) becomes 食べなくても (even if I do not eat).

運動うんどうしなくても、太ふとらない。

Even if I don’t exercise, I will not get fat.

彼かれは頭あたまがいいです。勉強べんきょうしなくても、試験しけんに合格ごうかくします。

He’s clever. Even if he doesn’t study he will pass the exam.

And we can apply the same grammar to adjectives.

試験しけんが難むずかしくても頑張がんばります。

Even if the exam is difficult I will do my best.

このブランドの品質ひんしつが悪わるくて、安やすくてもぜったい買かわない。

The quality of this brand is poor so even if it’s cheap I definitely won’t buy it.

6. Prohibition (“You must not”)

ここで写真しゃしんを撮とってはいけません。

You must not take pictures here.

そのケーキを食たべてはだめですよ。

You must not eat that cake.

Note: In spoken Japanese, ては is very frequently contracted to ちゃ. Therefore, 食べてはだめ becomes 食べちゃだめ.

The いけません is, in fact, the negative potential form of the verb “to go”. In other words, the literal translation for this usage would be:

〜てはいけません。

As for doing this action, it cannot go.

In this respect, it might help to think of the English idiom “that won’t do”, which is about as close to a natural but direct translation as you can get.

Of course, いけません does not have to be in the polite form.

美術館の中で　写真を　撮ってはいけない。

You must not take pictures inside the art museum.