When used with the verb stem そう expresses that something is likely to happen or be true based on your own first-hand experience or judgment.
| It looks like it’s going to rain. |
Context: You’ve looked up at the sky and seen dark clouds.
| It seems like it’s going to take some time, eh? |
Context: You think the task is going to be difficult.
| He’s got a look that says he’s interested in her, right? |
Context: You’re sat across the table and your friend keeps looking at the girl.
| ありそうな |
| A likely reason. |
We can connect the phrase to noun using な and to a verb using に.
| To almost hit an oncoming car. |
It can also be used with the potential.
| できそうですか。 |
| Do you reckon you can do it? (Does it seem like you can do it?) |
To make the sentence negative we add にない.
| できそうにない。 |
| It doesn’t seem I can do it |
そう can also be used with adjectives. For i-adjectives we need to get rid of the final い; for na-adjective we append そう without the な particle.
| An expensive-looking apartment. |
Context: You don’t know the rent but you’ve seen the luxury furnishings inside.
| ケーキがうまそう！ |
| The cake looks delicious! |
| A convenient-sounding system. |
Context: You’ve not used the system yourself, but you’ve read the details and can imagine it’s convenient.