Meaning of -ER in English

-ER

I. -er 1 /ə $ ər/ BrE AmE suffix

forms the comparative of many short adjectives and adverbs:

hot, hotter

dry, drier

fast, faster

⇨ ↑ -est

II. -er 2 BrE AmE suffix [in nouns]

1 . someone who does something or is doing something:

a dancer

a driver

2 . something that does something:

a scraper (=a tool you use for scraping)

⇨ ↑ -ar , ↑ -or

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.