- rudiment, first rudiment, first principle, alphabet, ABC, ABC's, ABCs - the elementary stages of any subject (usually plural); "he mastered only the rudiments of geometry"
--1 is a kind of fundamentals, basics, fundamental principle, basic principle, bedrock
- rudiment - the remains of a body part that was functional at an earlier stage of life; "Meckel's diverticulum is the rudiment of the embryonic yolk sac"
--2 is a kind of body part