Enact

enact stems from the Latin prefix en- meaning "to make; cause to be" plus the Latin root act- meaning "to do." Thus, enact means "to cause to be done" or, specifically, "to make into a law."
The Senate enacted a bill against air pollution.

A word based on enact is enactment, meaning "the passing of a law" or "a law that has been passed."
The Senate's enactment of the air pollution bill goes into effect today.

Actual

actual comes from the Latin word actus, "a doing", which is based on act- meaning "to do" and the Latin suffix -al which means "pertaining to; characterized by". Actual means "pertaining to something that is in action or in existence now"; thus, it means "existing; real"
What were his actual words?
Two words based on actual are actually, meaning "really" or "truly," and actuality, which means "reality; truth; fact."
What did he actually say?
Our dream of reaching the moon has become an actuality.

Actor

actor is formed from act- meaning "to do" and the Latin suffix -or meaning "a person who or a thing that perform an action." An actor is thus "a person who does something" or "a person who acts."
My son was an actor in the struggle, not an onlooker.
He was an actor in the play.
A word related to actor is its female form, actress.

Active

active comes from act- meaning "to do" plus the Latin suffix -ive which means "inclined to; tending to; having the character or quality of." Thus, active means "inclined to action; working; busy; lively."
She leads an active social life.
This is an active volcano.
One should have an active bank account.

Two words based on activee are activity and activate. Activity means "the state of being active; a particular action." Activate means "to make active or make capable of action."
There was little activity on the stock market today.
Can you activate this machine?

Agile

agile is made up of ag- meaning "to do" and the Latin suffix -ile which means "pertaining to; like; having the character or quality of." Thus, agile means "having the quality of doing or acting" or "able to do or move quickly and easily; nimble."
Peter is agile and athletic.
A word based on agile is agility, meaning "the ability to move quickly and easily."
The quarterback had remarkable agility.

Agent

agent comes from ag- meaning"to do" plus the Latin suffix -ent which means "a person who." Thus, agent means "a person who does something." This word is applied to someone who does a specific action or job, or who works for or represents an individual, company, or government bureau.

He is an FBI agent.
Does the actor have a press agent?
Does that company have a sales agent in our town?

A word based on agent is agency, meaning "a company, department or bureau that does a specific job or that represents other people or companies."

She works for an employment agency.

Agenda

agenda comes directly from a Latin word based on ag- meaning "to do" and means "a list of things to be done; a list of things to be discussed or decided upon."
There were three items on the agenda for the business meeting.