However, "promptus" is a Latin word, not a true English root. It means "ready" or "prepared." The prefix "im" is used to create the opposite meaning, so "impromptu" means "not prepared" or "unplanned".
Here's how the word evolved:
* Latin: *promptus* (ready, prepared)
* Middle English: *impromptu* (not ready, unplanned)
* Modern English: *impromptu* (unplanned, spontaneous)
So, while "promptus" is the source of the word, it's not a standard English root word in the way "graph" or "tele" might be.