Question

1. He gave us a signal to move forward.
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What is the relationship between 'signal' and 'to move forward'?
Are they in apposition? Or does 'to move forward' modify 'signal'?

Answer 1

Yes, they are in apposition.

"signal" is the direct object of the verb "gave" and "to move forward" is an infinitive phrase being used as an appositive for "signal."

Answer 2

I respectfully disagree. "to move" is, I think, a prepositional phrase used to modify "signal". "forward" modifies "move". It would be an appositive if the sentence was written: "The signal, to move forward, was given by the lieutenant." An appositive is an adjective or adjective phrase of description, set off by commas. "Glenda, fair and graceful, was the good witch." or "Glenda, of the East, was a good witch."

Answer 3

Sorry, Reed, but Writeacher is correct. Since "move" is a verb, not a noun, "to move" is an infinitive.

Ahh -- we old English teachers may have limited knowledge -- but we do know infinitives from prepositional phrases.