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

Still, price is the key factor, and if the strait remains in its current state of semi-closure, Kaneva predicts demand next year will fall to its lowest point since 2019. — Tim McDonnell, semafor.com, 10 Sep. 2026

After months of dealing with the trucks, some residents have joked that there should be a fee for every semi that winds up on their street. — Dillon Thomas, CBS News, 9 Sep. 2026

In the first season of the new format, three of the four teams who performed best from September to January made the semi-finals. — James Horncastle, New York Times, 8 Sep. 2026

The Prime Air plane came to rest beside a roadway near two semi-trucks, according to images from the scene. — Anthony Izaguirre, Chicago Tribune, 6 Sep. 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"