Is read a book A sentence?

No, "read a book" is not a complete sentence. It is a phrase that lacks a subject.

Here are some ways to make it a complete sentence:

* "I read a book." (Adding the subject "I")

* "She read a book." (Adding a different subject)

* "Read a book!" (Making it an imperative sentence)

* "The book was read." (Changing the structure to a passive sentence)