What is the difference between instant and instantaneous? Which is correct in this sentence?
It had an almost __ response time.
Based on the fact that manufacturers of instant coffee never call it ‘instantaneous coffee’ I would say that ‘instant’ modifies a noun referring to a thing, whereas ‘instantaneous’ modifies a noun referring to an event. Your example falls in a grey area between the two, because the noun ‘time’ can refer to either the duration before the response occurs or the event of the response’s occurrence.