Definition

1. Verb (transitive):
   • To have an effect on something or someone; to influence.
   • To take action as a result of or in accordance with something, such as information, advice, or a feeling.

Usage

• This verb is used to describe a situation where one thing (a person, an event, an idea) causes a change or has an impact on another.
• It is also used to describe the action of doing something because you have received specific information or instructions.
• It is followed by a direct object (the thing or person being influenced or acted on).

Examples

• Influence meaning:
  • The teacher's encouraging words acted upon the student, giving her the confidence to apply to university.
  • The new government policy will act upon the economy in several ways.
• Take action based on something:
  • The police acted upon the tip they received from an anonymous caller.
  • You should act upon your doctor's advice for a quicker recovery.

Advanced Usage

• "To act upon impulse": To do something suddenly without planning, based on a sudden desire or feeling.
  • He bought the expensive watch after acting upon a sudden impulse.
• The phrase can sometimes be used in formal or technical contexts, such as in science ("The acid acts upon the metal") or law ("The court will act upon the evidence presented").

Variants and Related Words

• Act on: This is a more common phrasal verb with the same meaning as "act upon." They are often interchangeable.
  • We must act on this information immediately.
• Influence (v): To affect or change someone or something.
• Affect (v): To produce a change in someone or something.

Synonyms

• Influence
• Affect
• Impact
• Work on
• Sway

Related Phrasal Verbs

• Act on: (See "Variants and Related Words" above).
• Follow up on: To take further action on something.
  • The manager promised to follow up on our complaint.

Related Idioms

• To act on/upon someone's behalf: To represent someone or do something for them.
  • As his lawyer, I am authorized to act on his behalf.

Verb

1. have and exert influence or effect
   • The artist's work influenced the young painter
   • She worked on her friends to support the political candidate