ac

IPA/ˌeɪ ˈsiː/
KK[ˈesˈi]IPA/ˌeɪ ˈsiː/

ac — abbreviation

1. a common short form used in speech, messages, and product listings for an air co

1.abbreviationB1
Definition

a common short form used in speech, messages, and product listings for an air conditioner or for the system that cools indoor air

Example

The hotel listing said AC was included in every room.

AC in hotel listings for room facilities

Saira turned the AC down after the baby fell asleep.

turn the AC down

Common collocations
  • central AC
  • AC unit
  • AC broke
  • AC included
  • turn the AC down
Synonyms
  • air conditioning

    the full form; more explicit and slightly more formal than AC

  • air conditioner

    usually names the machine itself rather than the whole cooling system

  • cooling

    broader word that can describe the effect without naming the equipment

Antonyms
  • heating

    warms a space instead of cooling it

Grammar Patterns

have AC

turn the AC up/down

AC in + room/building/car

AC is on/off

Usage Note

Often refers either to the machine itself or to the cooling system for a room, car, or building. In everyday speech, people commonly say 'the AC is on' or 'the AC broke' instead of using the full term.

Common Mistakes

The room has good air condition.
The room has good AC.
Use 'AC' or the full term 'air conditioning'; 'air condition' is not the normal noun.

2. a short form used in electrical talk for current that reverses direction again a

2.abbreviationC1
Definition

a short form used in electrical talk for current that reverses direction again and again as it moves through a circuit

Example

The wall socket provides AC, not the direct current from batteries.

AC contrasted with battery-powered direct current

Ezra learned that AC changes direction many times each second.

core property: current changes direction repeatedly

Common collocations
  • AC power
  • AC motor
  • AC socket
  • run on AC
  • convert AC to DC
Synonyms
  • alternating current

    the full form used when the abbreviation needs to be spelled out

  • AC power

    common technical phrase for electrical power delivered as alternating current

Antonyms

Grammar Patterns

run on AC

AC power

convert AC to DC

household AC

Usage Note

Usually appears in technical, classroom, or product-label contexts and is often contrasted with DC. Distinguish from sense 1, which is about cooling equipment in homes, vehicles, and buildings.

Common Mistakes

This battery supplies AC to the flashlight.
This battery supplies DC to the flashlight.
Batteries normally provide direct current, not alternating current.

Word family

  • air conditioning
    nounB1
  • air conditioner
    nounA2
  • alternating current
    nounC1

Synonym discussion

Sense: abbreviation/1

AC and A/C usually mean the same thing: a short form for air conditioning or for the machine that provides it. AC is common in speech, text messages, hotel listings, and appliance labels, while A/C is a written variant often seen in American advertisements and car controls. The full form air conditioning is clearer in formal descriptions or when you want to talk about the whole system rather than a quick convenience feature. In electrical contexts, however, AC usually points to sense 2, alternating current, so nearby words such as room, unit, power, or voltage tell you which meaning is intended.

AC ↗A/Cair conditioning

Common collocations

Nouns

Phrases

  • have AC
  • AC included
  • turn the AC down
  • run on AC
  • convert AC to DC

Prepositions

Etymology

English

AC is formed from the first letters of two English phrases: air conditioning and alternating current. The cooling meaning became common in the twentieth century as homes, cars, and offices increasingly used mechanical climate control. The electrical meaning developed in technical English for power that changes direction repeatedly in a circuit. Because the same two letters stand for both phrases, context determines which sense is meant.