semi

¹ American  

[sem-ee, sem-ahy] / ˈsɛm i, ˈsɛm aɪ /

noun

Informal.

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.

Etymology

Origin of semi¹

By shortening

Origin of semi-¹

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

Kodiak AI, a Mountain View-based tech company, is developing autonomous semi trucks it says will improve safety and efficiency on the roads.

From Los Angeles Times

The 24-year-old Italian and defending back-to-back Aussie champ fell to Djokovic in the semis, but he has won four majors of his own and has now split the last nine with Alcaraz.

From The Wall Street Journal

"I remember I was not sleeping well, semis, even quarters. Final I don't even... how many emotions and how many thoughts was going through my head," she said on Saturday, looking back to 2022.

From Barron's

“In short, while we acknowledge the established leadership of semis, the technical setup suggests software may be nearing an important inflection point in relative performance,” he said.

From Barron's

She had managed to press on to the semis only three times before, and never in Australia.

From Barron's