Invite Jim on our fishing trip.

In the above sentence can you tell me what words modify the predicate. I think
the predicate is invite but I'm not sure.
if so would on our fishing trip be the
predicate modifiers. And also would Jim be the subject of the sentence?

3 answers

Yes, "invite" is the simple predicate (the verb).

The whole sentence is the predicate. "Jim" is the direct object of "invite," and "on our fishing trip" is a adverbial prepositional phrase modifying "invite."

The subject is the understood (You).
You're right -- "invite" is the main verb. This is a command type of sentence (as opposed to a statement, a question, or an exclamation). Therefore, the subject is understood, not stated.

If the subject is not stated, then all the rest of the sentence is the complete predicate. "Jim" is the direct object.

http://english.unitecnology.ac.nz/resources/resources/exp_lang/sentence.html

Scroll down far enough to read about command (imperative) sentences.
wow didn't know that one, thanks!