English Reference
noun · adverb

semi

n. · adv.
US /ˈsɛmaɪ/ UK /sˈɛmi/ se·mi

  1. 01 B1 Intermediate British EnglishInformal

    n.a house that is joined to another house on one side.

    n.a semi-detached house, sharing one common wall with an adjacent property.

    Simple

    They live in a quiet semi at the end of the street.

    In context

    The developer converted the Victorian semi into two separate apartments, though the shared wall required significant soundproofing.

    Usage

    Commonly used in British and Australian English to describe residential property.

    semi detached
  2. 02 B1 Intermediate American EnglishInformal

    n.a very large truck used for carrying goods over long distances.

    n.a semi-trailer or tractor-trailer used for heavy haulage.

    Simple

    The highway was full of semis carrying supplies to the city.

    In context

    The driver struggled to manoeuvre the semi through the narrow industrial estate, eventually requiring a spotter to assist with the tight turn.

    Usage

    Primarily North American usage; the British equivalent is 'artic'.

    artictractor trailereighteen wheeler
  3. 03 B1 Intermediate Informal Sport

    n.a match or race that comes just before the final.

    n.a semi-final round in a knockout competition.

    Simple

    Our team won the semi and will play for the trophy on Sunday.

    In context

    After a gruelling semi that went into extra time, the players had only three days to recover before the championship match.

    semi final
  4. 04 C1 Advanced InformalTechnical Computing

    n.companies that make computer chips.

    n.shorthand for semiconductor companies or their stocks.

    Simple

    Investors are buying semis because of the high demand for AI chips.

    In context

    The portfolio manager increased exposure to the semis, betting that the supply chain constraints would ease by the third quarter.

    semiconductorchipmaker
  5. 05 C1 Advanced Slang

    n.a gun that fires one bullet each time you pull the trigger.

    n.a semiautomatic firearm.

    Simple

    The police found a semi hidden in the back of the car.

    In context

    The legislation specifically targets the sale of high-capacity semis to unlicensed individuals.

    semiautomatic
  6. 06 B2 Upper Intermediate Informal

    adv.partly or somewhat.

    adv.to some extent; partially.

    Simple

    I was only semi-conscious when the alarm went off this morning.

    In context

    The project was only semi-successful, as it met the technical requirements but failed to gain traction with the target audience.

    Usage

    Usually functions as a prefix, but used as a standalone adverb in very casual speech.


The prefix semi- (from Latin) used as a noun.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Level B2 · Upper Intermediate
Frequency Common
Updated