כאשר

Etymology
From ; compare.

Conjunction

 * 1) When, as, at the time that.

Usage notes

 * In modern use, this term is comparatively formal, the shorter synonym being comparatively informal.
 * Unlike English, is not used in framing questions, nor in introducing interrogative content clauses; the interrogative adverb and conjunction  is used for these purposes.
 * Whereas in English, and  are somewhat interchangeable in introducing complement clauses for temporal nouns — “the time when” and “the time that” being synonymous — in Hebrew  cannot be used this way; rather,  or (more frequently)  is required.