Impromptu vs Impromptus - What's the difference?

impromptu | impromptus |

As nouns the difference between impromptu and impromptus

is that impromptu is (music) a short musical composition for an informal occasion often with the character of improvisation and usually to be played solo while impromptus is .

As an adjective impromptu

is improvised; without prior preparation, planning or rehearsal; extemporaneous; unplanned.

Impromptus vs Extemporaneous - What's the difference?

impromptus | extemporaneous |

As an adjective extemporaneous is

without preparation or advanced thought; offhand.