Try Our Apps


Avoid these words. Seriously.


[sem-ee, sem-ahy] /ˈsɛm i, ˈsɛm aɪ/
noun, Informal.
semitrailer (def 1).
Often, semis. semifinal (def 3).
Origin of semi
by shortening


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.
Middle English < Latin sēmi-; cognate with Old English sōm-, sām- half (modern dial. sam-), Old High German sāmi-, Sanskrit sāmi-, Greek hēmi-; cf. sesqui-
Usage note
See bi-1. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
Cite This Source
Examples from the Web for semi
Contemporary Examples
Historical Examples
  • Clearly these should only be planted in wild and semi–wild places.

    The Wild Garden William Robinson
  • semi has had more success than I require, and considerably more than I expected.

    Miss Eden's Letters Emily Eden
  • semi can give him the former, and over the latter our future journey lies.

    Buffalo Land W. E. Webb
  • Raising his hand in a semi salute, the man started into the woods.

    The Clock Strikes Thirteen

    Mildred A. Wirt
  • It continues to be the resort of persons of every civilized, and almost every semi civilized, nation on the face of the earth.

British Dictionary definitions for semi


noun (pl) semis
(Brit) a semidetached house
short for semifinal
(US & Canadian, Austral & NZ) short for semitrailer


half: semicircle Compare demi- (sense 1), hemi-
partially, partly, not completely, or almost: semiprofessional, semifinal
occurring twice in a specified period of time: semiannual, semiweekly
Word Origin
from Latin; compare Old English sōm-, sām- half, Greek hēmi-
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
Cite This Source
Word Origin and History for semi


before vowels sem-, word-forming element meaning "half, part, partly; partial, imperfect; twice," from Latin semi- "half," from PIE *semi- "half" (cf. Sanskrit sami "half," Greek hemi- "half," Old English sam-, Gothic sami- "half").

Old English cognate sam- was used in such compounds as samhal "poor health," literally "half-whole;" samsoden "half-cooked," figuratively "stupid" (cf. half-baked); samcucu "half-dead," literally "half-alive;" and the last survivor of the group, sandblind "dim-sighted" (q.v.). Common in Latin (e.g. semi-gravis "half-drunk," semi-hora "half hour," semi-mortuus "half-dead," semi-nudus "half-naked," semi-vir "half-man, hermaphrodite"). The Latin-derived form in English has been active in forming native words since 15c.

Online Etymology Dictionary, © 2010 Douglas Harper
Cite This Source
semi in Medicine

semi- pref.

  1. Half: semicanal.

  2. Partial; partially: semiconscious.

  3. Resembling or having some of the characteristics of: semilunar.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Cite This Source
semi in Science
A prefix that means "half," (as in semicircle, half a circle) or "partly, somewhat, less than fully," (as in semiconscious, partly conscious).
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
Cite This Source

Word of the Day

Nearby words for semi

Difficulty index for semi

Many English speakers likely know this word

Word Value for semi

Scrabble Words With Friends