rudiments

(noun) a statement of fundamental facts or principles. Synonyms: basics.

(noun) the elementary stages of any subject (usually plural). Synonyms: rudiment, first rudiment, first principle, alphabet, ABC, ABC's, ABCs. Example: "He mastered only the rudiments of geometry."

(noun) the remains of a body part that was functional at an earlier stage of life. Synonyms: rudiment. Example: "Meckel's diverticulum is the rudiment of the embryonic yolk sac."