1. [ noun ] the elementary stages of any subject (usually plural)
Synonyms: first_principle abc's abcs alphabet first_rudiment rudiment

"he mastered the rudiments of geometry"

Related terms: fundamentals plural
2. [ noun ] a book designed to teach the alphabet by showing words starting with each letter
Synonyms: abecedary
Related terms: reader
3. [ noun ] a statement of fundamental facts or principles
Synonyms: ABC's ABCs rudiments basics
Related terms: fact
Similar spelling:   ABCs