sesqui-

1. a combining form meaning “one and a half,” used in the formation of compound words:

   sesquicentennial.

sesqui-

prefix

1. indicating one and a half

   sesquicentennial

2. (in a chemical compound) indicating a ratio of two to three

   sesquioxide

Word History and Origins

Origin of sesqui-¹

< Latin sēsqui- < *sēm ( i ) sque, equivalent to sēmis half-unit, semis + -que and (cognate with Greek té, Sanskrit ca, Gothic -uh )

Word History and Origins

Origin of sesqui-¹

from Latin, contraction of semi- + as as ² + -que and

Example Sentences

In 1961, a group of Black protesters, most of them local college students, attempted to the enter Sesqui, which was open to White visitors only.

From Washington Times

He has memories from growing up of visiting the park with family, but he never knew “Sesqui” had a campground.

From Washington Times

On a cool November morning - prime hiking weather - Hunter walked the trails of Sesqui with state parks Director Paul McCormack, discussing what’s become their shared mission: making state park campgrounds look more like the communities they serve.

From Washington Times

Its name: the Sesquicentennial Amphitheater, “Sesqui” for short.

From Washington Post

Sesqui-, Latin for one and a half; so Sesquipedalis, a foot and a half long.

From Project Gutenberg

Words That Use sesqui-

What does sesqui- mean?

Sesqui– is a combining form used like a prefix meaning “one and a half.” It is occasionally used in scientific terms, especially in chemistry.

Sesqui– comes from Latin and is equivalent to sēmis, meaning “half-unit,” and –que, a suffix meaning “and.” The Greek cognate of sēmis is hēmi-, meaning “half,” which is the source of terms such as hemisphere. To learn more, check out our Words That Use article on the combining form hemi-.

Examples of sesqui-

One example of a technical term that uses sesqui– is sesquicentennial, “pertaining to or marking the completion of a period of 150 years.”

The sesqui– part of the word means “one and a half,” as we know. The word centennial may also seem familiar; it means “pertaining to a period of 100 years.” Sesquicentennial literally translates to “pertaining to a period of 150 years.”

What are some words that use the combining form sesqui-?

• sesquialtera
• sesquicarbonate
• sesquihydrate
• sesquioxide
• sesquipedalian (using the equivalent form of sesqui– in Latin)
• sesquiplane

What are some other forms that sesqui– may be commonly confused with?

• -esque
• septi-
• septo-

Break it down!

Sesquipedalian means “given to using long words.” The suffix –pedalian means roughly “measuring a foot.” Given the meaning of sesqui-, what does sesquipedalian literally translate to?