"rudiments" in the noun sense
1. 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. rudiments, first principles, alphabet, ABC, ABC's, ABCs
the elementary stages of any subject (usually plural
"he mastered only the rudiments of geometry"
Source: WordNet® (An amazing lexical database of English)
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