expression, conjunction
only because ...; precisely because
Attaches to the -ba conditional stem of a verb to emphasize that the stated reason is the sole or decisive cause. Often used in formal or written Japanese. Compare からこそ, which attaches to the plain form.
See also: からこそ
努力すればこそ、成功できたのだ。
It is precisely because I made an effort that I was able to succeed.
君のことを思えばこそ、厳しく言っているんだ。
It is exactly because I care about you that I'm being strict.
expression
definitely not; certainly not
Used with the negative -nai stem of a verb, often in patterns like 〜も...ばこそ or 〜など...ばこそ, to strongly deny something. Literary and somewhat archaic.
彼の言うことなど信じらればこそ。
I certainly cannot believe what he says.
そんな難しい問題が解けばこそ。
There's no way I can solve such a difficult problem.
expression
if actually; if it is the case that
Rare, archaic conditional use. Expresses 'if it is true that...' or 'supposing that...'. Not used in modern colloquial Japanese.
昔の文語では、「行かばこそ」のように仮定を表した。
In classical literary language, forms like 行かばこそ expressed a supposition.