semi

1 of 4

noun (1)

ˈse-ˌmī 

also

-mē 

plural semis

: semifinal

—often plural

semi

2 of 4

noun (2)

ˈse-ˌmī 

also

-mē 

plural semis

: semitrailer

semi

3 of 4

noun (3)

ˈse-mē 

also

-ˌmī 

plural semis

chiefly British

: a semidetached house

semi-

4 of 4

prefix

ˌse-mē, 

-ˌmī, 

-mi

1

a

: precisely half of:

(1)

: forming a bisection of

semicircle

(2)

: being a usually vertically bisected form of (a specified architectural feature)

semidome

b

: half in quantity or value : half of or occurring halfway through a specified period of time

semiannual

semimonthly

compare bi-

2

: to some extent : partly : incompletely

semi-independent

semidry

compare demi-, hemi-

3

a

: partial : incomplete

semiconsciousness

semidarkness

b

: having some of the characteristics of

semiporcelain

c

: quasi-

semigovernmental

semimonastic

Examples of semi in a Sentence

Recent Examples on the Web

Noun

The initial investigation shows the trooper was partially blocking the left lane of travel while tow trucks were removing the semi from the center median. — Jennifer McRae, CBS News, 14 Oct. 2026

As part of the agreement, Netflix will make one match per day available for free in Spain and will sublicense a package of matches, including every Spain match, both semi-finals and the final, to a national free-to-air broadcaster. — Scott Roxborough, HollywoodReporter, 13 Oct. 2026

If a semi can travel hundreds of highway miles without a person in the cab, what happens to the person who used to sit there? — Kurt Knutsson, FOXNews.com, 12 Oct. 2026

Acts who might typically tour with multiple semi-trucks have to pare it down to come play the off-the-grid, experimental fest. — Katie Bain, Billboard, 8 Oct. 2026

Word History

Etymology

Noun (3)

short for semidetached

Prefix

Middle English, from Latin; akin to Old High German sāmi- half, Greek hēmi-

First Known Use

Noun (1)

1942, in the meaning defined above

Noun (2)

1942, in the meaning defined above

Noun (3)

1912, in the meaning defined above

Phrases Containing semi

• semi-antique
• semi-autobiographical
• semi-autobiography
• semi-erect
• semi-independent
• semi-private
• semi-skimmed milk

Rhymes for semi

• emmy
• jemmy
• remi

Kids Definition

semi-

prefix

ˌsem-i, 

ˈsem-, 

-ˌī

1

: half in amount or value

semitone

2

: occurring halfway through a certain time period

semiannual

3

: to some extent : partly : incompletely

semitropical

4

: partial : incomplete

semidarkness

Etymology

Prefix

Latin semi- "half"