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semi

1 American  
[sem-ee, sem-ahy] / ˈsɛm i, ˈsɛm aɪ /

noun

Informal.

  1. semitrailer.

  2. Often semifinal.

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.
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
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
semi 2 British  
/ ˈsɛmɪ /

noun

  1. a semidetached house

  2. short for semifinal

  3. short for semitrailer

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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).

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.

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-; sesqui-

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

But their run to the Europa League semis in the previous campaign will give them belief - and provide hope to every small club of what can still be achieved in Uefa's major competitions.

From BBC

This adaptation appears repeatedly in the fossil record among fish eating animals, including aquatic ichthyosaurs, semi aquatic crocodile and flying pterosaurs.

From Science Daily

They could be without captain Sidney Crosby, who was forced off in their last eight win over Czech Republic with a knee injury and missed the Finland semi.

From BBC

Furthermore, they boast an excellent record against the Canadians and beat them in last year's world semis.

From BBC

They were missing leader Marie-Philip Poulin in their opening loss to the U.S., and the U.S. can turn flat, like they did in a sleepy second-period chunk of the semi against Sweden.

From The Wall Street Journal

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.