Third-party and Third person

Third person and third-party are semantically related. In some cases you can use "Third person" instead a noun phrase "Third-party".

Third person noun - Pronouns and verbs that are used to refer to something other than the speaker or addressee of the language in which they occur.

Third-party and third person are semantically related. Sometimes you can replace phrase "Third-party" with "Third person", this phrases are similar.