Which is grammatically correct has sent or send?

The grammatically correct form depends on the tense of the sentence:

* Has sent is the present perfect tense. It describes an action that started in the past and continues to have an effect in the present.

* Example: "She has sent the email."

* Send is the present tense. It describes an action happening now.

* Example: "Please send me the document."

* Sent is the past tense. It describes an action that happened in the past.

* Example: "He sent the package yesterday."

So, the correct form depends on the context and the intended meaning.