Let's do lunch some time next week.
The sentence is not, because an idiom is usually a phrase. The idiom is "do lunch," which means to have lunch together, usually while discussing business.
My Favorite IDIOM Is, When Pigs Fly.
Idiom
The prepositional phrase in the sentence is "for lunch."
To include an idiom in an example sentence, simply incorporate the idiom naturally into the sentence to convey a figurative meaning. For example, "She had a chip on her shoulder" is an idiom meaning she was easily offended or held a grudge.
An idiom usually is a sentence, or part of one. It certainly can be used as part of a sentence. The way to tell if it's an idiom is if it makes sense the way it's literally written.
That IS a sentence.
"Throw the book at him" IS a sentence.
yes
Yes, this is a run-on sentence, because it contains two independent clauses (each can stand alone as a sentence) that are not separated by any punctuation or conjunction.The following are examples of how to correct this error:Before lunch you played volleyball. After lunch you played again.Before lunch you played volleyball; after lunch you played again.Before lunch you played volleyball, and after lunch you played again.
The object of the preposition 'for' is lunch.
"Hit the books" is a sentence.