Particle
it is ... that ...; precisely; in particular; definitely; for sure; only (when, after, because, etc.)
emphasizes preceding word or phrase
辛抱こそ大事なんだ。It's patience that counts. although; while; it is the case that ... but
as こそあれ, こそすれ, こそするが, etc.
it is precisely because ... that ...; only because ...
after conditional -ba form of verb
not at all; not in the slightest; absolutely not; never
Formal or literary termafter -nai stem of verb + ば