ABCs ABCs /ˌeɪbiːˈsiːz/

noun

1. The elementary stages of any subject (usually plural)  ( ABC , ABC's , ABCs , alphabet , first principles , rudiments )
   the elementary stages of any subject (usually plural)
    He mastered only the rudiments of geometry
   he mastered only the rudiments of geometry
   

 ABC ABC /ˌeɪbiːˈsiː/

noun

1. The elementary stages of any subject (usually plural)  ( ABC , ABC's , ABCs , alphabet , first principles , rudiments )
   the elementary stages of any subject (usually plural)
    He mastered only the rudiments of geometry
   he mastered only the rudiments of geometry