I'm writing a book, and I don't know if I'm using the word peoples right. I'm fairly sure it IS a word, but I don't know its exact use.
That use seems fine, something like "ancient Europe was inhabited by peoples of varied language and cultural."
Wiktionary has: (plural peoples) Persons forming or belonging to a particular group, such as a nation, class, ethnic group, country, family, etc; folk; community. wiktionary
Peoples can be used with the meaning you are suggesting:
- As a term meaning "a body of persons sharing a culture," people is a singular noun, as in As a people the Pueblo were noteworthy for their peacefulness. Its plural is peoples: the many and varied peoples of West Africa. But when used to mean "humans," people is plural and has no corresponding singular form. English is not unique in this respect; Spanish, Italian, Russian, and many other languages have a plural word meaning "people" that has no singular.
an alternative can be
The total number of inhabitants constituting a particular race, class, or group in a specified area.
- A group of individuals of the same species occupying a particular geographic area. Populations may be relatively small and closed, as on an island or in a valley, or they may be more diffuse and without a clear boundary between them and a neighboring population of the same species. For species that reproduce sexually, the members of a population interbreed either exclusively with members of their own population or, where populations intergrade, to a greater degree than with members of other populations.