Save This Word!

a combining form meaning “one and a half,” used in the formation of compound words: sesquicentennial.
In effect, this quiz will prove whether or not you have the skills to know the difference between “affect” and “effect.”
Question 1 of 7
The rainy weather could not ________ my elated spirits on my graduation day.
Meet Grammar CoachWrite or paste your essay, email, or story into Grammar Coach and get grammar helpImprove Your Writing
Meet Grammar CoachImprove Your Writing
Write or paste your essay, email, or story into Grammar Coach and get grammar help

Origin of sesqui-

<Latin sēsqui-<*sēm(i)sque, equivalent to sēmis half-unit, semis + -que and (cognate with Greek té,Sanskrit ca,Gothic -uh)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022

How to use sesqui- in a sentence

  • At length it was discovered that sesqui-sulphide of phosphorus would make just as good matches and was harmless.

    Makers of Many Things|Eva March Tappan
  • We may, for example, differentiate in this way the alkaline bicarbonates from the sesqui-carbonates or the carbonates.

    The Mechanism of Life|Stphane Leduc
  • Float the paper on a solution of the sesqui-chloride of iron.

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

British Dictionary definitions for sesqui-


indicating one and a halfsesquicentennial
(in a chemical compound) indicating a ratio of two to threesesquioxide

Word Origin for sesqui-

from Latin, contraction of semi- + as as ² + -que and
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012