"Send" is the root word, and it means to cause to go or be taken to a destination, often by mail, email, or messenger.
Here are some examples of how "send" is used:
* I sent you a letter.
* Please send me the document.
* The company will send a representative to meet with you.
While "sent" itself is not a root word, it is derived from the root word "send" and carries the same core meaning of transmission or dispatch.