act
UK[ækt]US[ækt]
v
To do something for a particular purpose or in a particular way.
v
To behave in a particular way, especially a way that seems unusual or surprising.
v
To perform a part in a play, film, or television show.
n
A single thing that someone does.
n
A law that has been officially accepted by a parliament or similar group.
n
One of the main divisions of a play or opera.
Etymology
The English word 'act' entered the language in the late 14th century from the Old French 'acte', meaning a formal document or decree, which itself derived from the Latin 'actum', meaning "a thing done" or "a performance." This Latin noun originates from the past participle 'actus' of the verb 'agere', meaning "to set in motion, drive, do, perform." The Proto-Indo-European root is believed to be ag-, signifying "to drive, draw out or forth, move." The core semantic journey is from the physical concept of driving or setting in motion, to the legal and formal concept of a documented deed, and finally to the broad modern senses of performing, doing, and behaving, as well as the specific theatrical and legislative meanings.
Analysis
The word 'act' is a simplex word borrowed as a whole from Latin. It does not contain separable, meaningful sub-parts within its modern English spelling.
Examples
The government must act quickly to address the crisis.
She acted surprised when she heard the news, though she already knew.
The second act of the play was the most dramatic.