A very brief moment; an instant. Often used in literary or poetic contexts; can function adverbially (e.g., 刹那に).
刹那、彼女の顔に笑みが浮かんだ。
For an instant, a smile appeared on her face.
決断は刹那のうちに下さなければならない。
The decision must be made in an instant.
光は刹那にして消えた。
The light vanished in an instant.
彼は刹那の迷いもなく行動した。
He acted without a moment's hesitation.
In Buddhism, a kṣaṇa — the shortest unit of time in which a single mental event lasts (traditionally about 1/75 of a second). A technical, doctrinal sense.
経典によれば、刹那は心が変化する最小の時間単位とされる。
According to the sutras, a kṣaṇa is considered the smallest unit of time in which the mind changes.
仏教哲学では、存在は諸刹那の連続として説明されることが多い。
In Buddhist philosophy, existence is often explained as a succession of kṣaṇas.