Can you add php include to template?

Can you add a normal php include statement to a WordPress template file?

Sorry if that’s a dumb / obvious question.

And if it was a javascript file would it look like this…

<?php include “scripts/contact.js”; ?>

or is that completely wrong?

OR….

can I just paste this code into the contact page template right before the get_header()

<script src=”http://my-site.com/wp-site/scripts/contact.js”></script&gt;