semi

¹

[sem-ee, sem-ahy]

noun

Informal.

1. semitrailer.

2. Often semifinal.

semi-

²

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

/ ˈsɛmɪ /

noun

1. a semidetached house

2. short for semifinal

3. short for semitrailer

semi-

²

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

semi–

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

Confusables Note

See bi- ¹.

Word History and Origins

Origin of semi–¹

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-

Word History and Origins

Origin of semi–¹

from Latin; compare Old English sōm-, sām- half, Greek hēmi-

Example Sentences

This was a repeat of the 2023 World Cup semi final won by Spain 2-1 en route to being crowned champions.

Read more on Barron's

England did not need to win this game to reach the semis - they play Australia next on Wednesday, who look close to unbeatable, followed by New Zealand where they would be strong favourites.

Read more on BBC

And at Wimbledon, she came unstuck in a semi.

Read more on The Wall Street Journal

"Up until the semi finals, it seemed like nothing would be able to stop Grok 4 on its way to winning the event," Pedro Pinhata, a writer for Chess.com, said in its coverage.

Read more on BBC

Mboko hurt her hand in the semi against Rybakina in a heavy fall in Montreal, but says she doesn't feel it ahead of the final.

Read more on BBC

When To Use

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.