First, you need to understand that the point of an idiom is to give a figurative picture to express a thought. For example, instead of saying "he died, " the speaker says, "he kicked the bucket, " or "stay positive" becomes "keep your head up." None of these are meant to be literal that is why language can be difficult for a new speaker to understand. All languages have them but a native speaker may take the saying for granted and not realize the quandary created for the non-native speaker.
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.
Let's do lunch some time next week.
My Favorite IDIOM Is, When Pigs Fly.
Idiom
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
This is not an idiom. The verb "lay" is the past tense of "lie," and means that whatever or whoever the subject of the sentence may be, they were laying down on top of some hay.
"Hit the books" is a sentence.
fall a prey