D defs.my
Entry 2 senses Webster, 1913

-er

/(-ẽr)/ · IPA /ɚ/
01 The termination of many English words, denoting the agent; -- applied either to men or things; as in hater, farmer, heater, grater. At the …
  1. 1.
    The termination of many English words, denoting the agent; -- applied either to men or things; as in hater, farmer, heater, grater. At the end of names of places, -er signifies a man of the place; as, Londoner, i. e., London man.
  2. 2.
    A suffix used to form the comparative degree of adjectives and adverbs; as, warmer, sooner, lat(e)er, earl(y)ier.