Meaning of -IN in English

-IN

~ 1

■ suffix Chemistry forming names of organic compounds, pharmaceutical products, proteins, etc: insulin.

Origin

alt. of ~e 4 .

————————

~ 2

■ combining form denoting a gathering of people for a common purpose, typically as a form of protest: sit~.

Concise Oxford English vocab.      Сжатый оксфордский словарь английского языка.