- imperceptible (adj.)
[imperceptible 词源字典]
- early 15c., from French imperceptible (early 15c.), from Medieval Latin imperceptibilis, from assimilated form of in- "not, opposite of" (see in- (1)) + perceptibilis (see perceptible). Related: Imperceptibly. OED marks imperceivable as "Now rare."[imperceptible etymology, imperceptible origin, 英语词源]