What is the prefix of extend?

Answer 1

I had to check a few sources on this one, but the prefix is "ex-."

Tend means, "Regularly or frequently behave in a particular way or have a certain characteristic.

The prefix "ex-" means "out, away from, outside."

So outside of what tends to be normal.

Answer 2

The past participle of the verb to extend is extended, which can be an adjective. It has the rarely-seen adverb form extendedly. The related noun extension has an adverb form extensionally.

Much more common is the adverb form of extensive, which is extensively, with a different connotation than extending.

Answer 3

The noun forms of the verb to extend are extender, extension, and the gerund, extending.