そう Look like, Appear, Seem, Have a feeling that

そう is used to express that something seems likely based on perception or indirect signs, e.g. 雨が降りそう ('It looks like it's going to rain.'). In contrast, そうもない (or そうにない) indicates that there are no signs of something happening, e.g. 雨が降りそうもない ('It doesn't seem like it'll rain at all.').

そう expresses that something appears a certain way based on perception or indirect signs, e.g. 雨が降りそう ('It looks like it'll rain.'). In contrast, そうにない (or そうもない) indicates that something shows no signs of happening, e.g. 雨が降りそうにない ('It doesn't seem like it'll rain at all.').

The たい form expresses personal desires, such as 日本に行きたい ('I want to go to Japan'), though, the たい form is typically not used for expressing others' desires. One way that we can comment on another person's desires, however, is to use the そう form, meaning 'appears to.' For example 日本に行きたそう can be used to mean 'They seem to want to go to Japan.'

The main difference between そう and らしい① lies in the source of information. そう implies speculation based on personal observation, e.g. 面白そう ('It looks interesting.'). らしい is based on secondhand information or inference, e.g. 面白いらしい ('I hear it's interesting.' or 'Apparently, it's interesting.').

ような気がする and そう both express impressions, but with different nuance. ような気がする conveys personal intuition or vague feeling, i.e. something you sense even without clear reason. On the other hand, そう is typically based on observable clues or appearance. In that sense, ような気がする is more subjective and less confident than そう.

Both っぽい and そう express appearance or impression, but differ in nuance and usage. そう attaches to word stems and is neutral and often based on observation, e.g. 雨が降りそう ('It looks like it'll rain.'). っぽい is casual and attaches to nouns to mean '~ish' or '~like', e.g. 子供っぽい 'childish'. Unlike そう, it often carries a negative or demeaning tone.

のように・のような and そう both express impressions, but with different nuance. のように・のような show direct comparison, like 'like' or 'as if,' e.g. 春のように暖かい ('It's warm like spring.'). そう expresses a perceived impression based on observation, e.g. 暖かそう ('It seems warm.').

Both みたい and そう can mean 'seems like', but differ in nuance and usage. みたい compares something to another, e.g. 春みたい ('It's like spring.') or is based on reliable evidence, e.g. 面白いみたい ('Apparently it's interesting.' i.e. based on something you've heard). そう is based on appearance or sensory impression, e.g. 面白そう ('It looks/sounds interesting.').

にみえる and そう both express that something 'seems' a certain way, but with different nuance. にみえる specifically refers to visual appearance and can be combined with そう, e.g. 面白そうにみえる ('It looks interesting.'). そう alone expresses general impression and doesn't necessarily rely on visual cues, e.g. 面白そう ('It seems interesting.'), which could be based on hearing about it, etc.

ように・ような and そう both convey impressions, but with different nuance. ように・ような expresses direct comparison or similarity, like 'as if' or 'like,' e.g. 春が来たように暖かい ('It's warm as if spring had come.'). そう is based on the speaker's observation or feeling, e.g. 暖かそう ('It seems warm.').