According to this site, faculty can be expressed in both singular and plural forms depending on which one you use. Then when I search up faculties, it exists. Why? Why is there the need of faculties when faculty does the job of being both a plural and singular form?
Faculty has two meanings (from Google):
an inherent mental or physical power.
the teaching staff of a university or college, or of one of its departments or divisions, viewed as a body.
If meaning 2 is intended, plural verbs even when talking about one faculty, because the noun refers to a collection of multiple people.
If meaning 1 is intended, you'd use a singular noun/verb if the subject is one faculty, and a plural noun/verb if the subject is multiple faculties.
When you see faculties, it's very likely meaning 1, although it's possible the word could be used to refer to multiple separate "teaching staffs of universities or colleges."
Its very simple if you are referring within single organization or University.... FACULTY is complete word for both single & multiple teachers as a collective Noun. However, if you are referring multiple organizations or Universities... FACULTIES is suitable word to refer different teachers from different Universities as a plural form of collective noun.
Just take Example of one more collective Noun... Team & Teams. I think now you can understand this better.
"Faculty", can refer to all the teachers of an organization only if by that word and on that occasion the entire teaching staff is addressed.if a few from each department or various departments are addresed,it's better to use "faculties". Eg The Faculty of xyz engg college went on a strike....is right. Five faculties,two from Chemistry department and three from the Mechanical department had refused to participate in the strike.
Both examples are right.