rudiment has definitions from the field of zoology
1
[ noun ] the elementary stages of any subject (usually plural)

Examples

"he mastered the rudiments of geometry"

Related terms

fundamentals plural

2
[ noun ] (zoology) the remains of a body part that was functional at an earlier stage of life

Examples

"Meckel's diverticulum is the rudiment of the embryonic yolk sac"

Related terms

body_part

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