act
[to do something]
He acted immediately to stop the fight.
activist
[one who seeks change through action]
The activist worked hard to change the law.
actor
[someone acting in a play or show]
That actor frightened me.
add
[(1) to put (something) with another to make it larger; (2) to say more]
Please add my name to the list. (1)
She told him to leave, but added that she would like to see him again. (2)
administration
[the executive part of a government, usually headed by a president or prime minister]
The new administration starts work in January.