-er

(a suffix with a variety of applications)

-er1
1. A suffix meaning a person or thing that does something, player, teacher; is something, foreigner; lives somewhere, villager; makes or works with something, hatter, butler, grocer; has something, rancher, double-decker; or is connected with or involved in something, first-grader.
2. This -er is used to form nouns either from verbs, as burner, climber, player, thinker; or from other nouns, as rancher, cottager, outsider, New Yorker.
-er2
A suffix forming the comparative degree of adjectives, as in cooler, softer, smoother; and of adverbs, as in slower.
-er3
A suffix meaning frequently, again and again, in verbs; such as, flicker, glimmer, patter, clatter, flutter, jabber, and putter.