What part of speech is the word 'each'?

Its a homonym for the last four letters eech.

–adjective

1.

every one of two or more considered individually or one by one: each stone in a building; a hallway with a door at each end.

or

–pronoun

2.

every one individually; each one: Each had a different solution to the problem.

or

–adverb

3.

to, from, or for each; apiece: They cost a dollar each.

it's adjective, pronoun and adverb.