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• semi
  semi

  noun

  semitrailer.
• semi-
  semi-

  a combining form borrowed from Latin, meaning “half,” freely prefixed to English words of any origin, now sometimes with the senses “partially,” “incompletely,” “somewhat”.
• semi–
  semi–

  A prefix that means “half,” (as in semicircle, half a circle) or “partly, somewhat, less than fully,” (as in semiconscious, partly conscious).

semi

¹ American  

[sem-ee, sem-ahy] / ˈsɛm i, ˈsɛm aɪ /

noun

Informal.

• semis
  plural

1. semitrailer.

2. Often semifinal.

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semi- ² American  

1. a combining form borrowed from Latin, meaning “half,” freely prefixed to English words of any origin, now sometimes with the senses “partially,” “incompletely,” “somewhat”.

   semiautomatic; semidetached; semimonthly; semisophisticated.

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semi- ¹ British  

prefix

1. half Compare demi- hemi-

   semicircle

2. partially, partly, not completely, or almost

   semiprofessional

   semifinal

3. occurring twice in a specified period of time

   semiannual

   semiweekly

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semi ² British  

/ ˈsɛmɪ /

noun

1. a semidetached house

2. short for semifinal

3. short for semitrailer

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semi– Scientific  

1. A prefix that means “half,” (as in semicircle, half a circle) or “partly, somewhat, less than fully,” (as in semiconscious, partly conscious).

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Usage

What does semi- mean? Semi- is a combining form used like a prefix meaning “half.” In some instances, it is used figuratively to mean "partially," "incompletely," or "somewhat." It is often used in a variety of technical and everyday terms. Semi- comes from Latin sēmi-, meaning “half.” The Greek cognate of sēmi- is hēmi-, also meaning “half,” which is the source of English terms such as hemialgia and hemicardia. To learn more, check out our entries for both words.

Commonly Confused

See bi- ¹.

Other Word Forms

Noun Inflected Forms

• semis
  plural

Etymology

Origin of semi¹

By shortening

Origin of semi-²

Middle English < Latin sēmi-; cognate with Old English sōm-, sām- half (modern dial. sam- ), Old High German sāmi-, Sanskrit sāmi-, Greek hēmi-; cf. sesqui-

Example Sentences

See Examples For:

semi semi- semi– semis

Johnny Beig may have played in a semi professional cricket league in Australia, but this summer he’s a big fan of soccer in the United States.

From Los Angeles Times ● Jul. 3, 2026

It was the first time Forest had reached a European semi final since 1984, while Forest's 5-0 win at Sunderland was their biggest away victory in the top flight since 1995.

From BBC ● Jul. 1, 2026

“Some investors may be concluding that Mr. Durn’s departure for a semi company is an indication of that sector having a greater opportunity,” D.A.

From MarketWatch ● Jun. 12, 2026

And on its way to the final, the club averaged 2.75 goals per game, even putting five past Bayern Munich in the first leg of their semi.

From The Wall Street Journal ● May 30, 2026

Tomás jogged over to the semi and fired it up.

From "Storm Runners" by Roland Smith

He “did not adopt a reflexive posture to protect himself and ... he may have fallen in a state of semi- or total unconsciousness,” officials said.

From Los Angeles Times ● Nov. 20, 2024

Semi-pedestal sinks are wall-hung sinks with a semi- or half-pedestal attached to the bottom of the sink.

From Seattle Times ● Feb. 28, 2022

The Emirati-Israeli unmanned vessels would be able to operate semi- and fully autonomously and carry out missions including submarine detection and anti-submarine warfare.

From Reuters ● Nov. 18, 2021

He's doubled it in a course of almost eight years, seven-and-a-half years, to be semi- exact.

From Washington Post ● Sep. 26, 2016

These had been grown elsewhere, because few crops could be raised in the dry semi- desert region of Loun-Ariik.

From "A Long Walk to Water" by Linda Sue Park

Whole vase covered with thin semi– lustrous wash varying from red–brown to black.

From How to Observe in Archaeology by Various

Wilson and his team said they prefer hyperscalers over semis for the next several months, though the former has gained a 30% edge over chips in three weeks, so “risk/reward is less attractive.”

From MarketWatch ● Jul. 20, 2026

Is France against Spain on Tuesday in the semis the real final, as many are suggesting?

From BBC ● Jul. 14, 2026

"Jude shines as England beat Norway 2-1 to reach semis", is the paper's review.

From BBC ● Jul. 12, 2026

The report concludes that ”any pullback in memory semis stocks is likely temporary.”

From MarketWatch ● Jul. 6, 2026

I made it through the morning, but I was beaten in the semis and ended up in third place.

From "Ugly" by Robert Hoge

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