Definition of -er suffix from the Oxford Advanced American Dictionary

-er

suffix
/ər/
 
 
1 (in nouns) a person or thing thatlovercomputer compare -ar, -ee, -or2 (in nouns) a person or thing that has the thing or quality mentionedthree-wheelerforeigner3 (in nouns) a person concerned withastronomerphilosopher4 (in nouns) a person belonging toNew Yorker5 (makes comparative adjectives and adverbs)widerbiggerhappiersooner compare -est