What part of speech is preforms?

Preforms can be categorized as a noun and a verb.

Parts of speech

1. preforms is a verb, present, 3rd person singular of preform (infinitive).
2. preforms is a noun, plural of preform.

Verb
preform - form or shape beforehand or determine the shape of beforehand
preform - form into a shape resembling the final, desired one
Noun
preform - An object that has undergone preliminary shaping but is not yet in its final form.
preform - The rough, incomplete and unused basic form of a stone tool.
preform - A word that is no longer in use, but has been reconstructed from current ones.