semi

1 of 4

noun (1)

ˈse-ˌmī 

also

-mē 

plural semis

: semifinal

—often used in 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

Three semi-trucks erupted in flames after a crash that killed one on the NJ Turnpike during the Thursday morning commute, according to New Jersey Transit CEO Kris Kolluri. — Alexa Herrera, CBS News, 25 June 2026

The 51% fault bar has made the initial investigation and blame allocation in crashes involving semi-trucks, delivery vans, and rideshare vehicles like Uber and Lyft increasingly important. — Matthew Kayser, Miami Herald, 25 June 2026

The format escalates through semi-finals and a final scheduled for June 25, intensifying constraints to simulate high-pressure competitive conditions. — Jijo Malayil, Interesting Engineering, 24 June 2026

The semi-finals are set to happen on July 14 and July 15. — Jibin Joseph, PC Magazine, 23 June 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"