Like は and も, the possessive particle の can also append itself to other particles to help modify nouns.
友達へ 手紙を 送ります。
To send a letter to a friend.
友達の 手紙。
A friend’s letter.
友達への 手紙。
A letter to a friend.
Note that にの is not a valid combination. We must use へ if we want to combine the directional particle with の!
友達から 手紙を もらいます。
To receive a letter from a friend.
友達からの 手紙。
A letter from a friend.
先生と 会話を します。
To have a conversation with a teacher.
先生との 会話。
A conversation with a teacher.
電車で 通勤します。
To commute by train.
電車での 通勤。
A commute by train.
東京から 京都までの 距離は およそ３８０キロメートルです。
The distance from Tokyo to Kyoto is about 380 kilometres.
Why do we do this? By appending の to these particles, we turn an action into a “noun block”. This allows us to make that block the topic or subject of a new sentence. For example, by turning “to have a conversation with a teacher” into “a conversation with a teacher”, we can now say:
先生との 会話は 面白いです
A conversation with a teacher is interesting.
In writing you may occasionally see へと used in combination but this does not change the meaning or grammatical usage. This will not appear on the N5 or N4, but you may see it later.
日本は、２０世紀に 産業社会から 技術社会へと 変りました。
During the 20th century, Japan moved from an industrial society to a technological one.