Adj-i[stem] + そう
Adj-na + そう
V[stem] + そう
Exceptions:
Negative:
Adj-i
Adj-na
V[stem] + そう + に/も + ない
~そう is used to express that something looks like or seems like a certain way based on its appearance. It is a subjective judgment based on what the speaker sees or feels.
It expresses conjectures about the present state or a future event. However, it cannot be used to express a conjecture about the past.
Grammatically, そう is a na-adjective: