What adjective means “having three parts”?

Solution 1:

Tripartite works, though it rings of the Tripartite Pact.

Merriam-Webster gives the following definition:

1 : divided into or composed of three parts
2 : having three corresponding parts or copies
3 : made between or involving three parties <a tripartite treaty>

The Tripartite Pact was the treaty that bound the Axis together in World War II. This causes tripartite to connote fascism. Needless to say, victor’s history makes this a very negative connotation. In contexts outside of history and politics, and especially in technical ones, the word is overall less connotative.