What is once in a minute, twice in a moment, and never in a thousand years?

Which letter of the alphabet fits this description?

M because there is one m in minute, two m's in moment, and no m's in a thousand years.

The answer to the riddle "What is once in a minute, twice in a moment, and never in a thousand years?" is the letter "M".

To understand why, let's break down the riddle:
- "Once in a minute": The letter "M" appears once in the word "minute" at the beginning.
- "Twice in a moment": The letter "M" appears twice in the word "moment" - once at the beginning and again in the middle.
- "Never in a thousand years": The letter "M" is not present in the phrase "a thousand years".

Therefore, the letter "M" fits all the given criteria and is the correct answer to the riddle.