a combining form meaning “night,” used in the formation of compound words: noctilucent.



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Also especially before a vowel, noct-.

Origin of nocti-

<Latin nocti-, combining form of noxnight Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021


What does nocti- mean?

Nocti- is a combining form used like a prefix meaning “night.” It is occasionally used in scientific terms.

Nocti- comes from the Latin nox, meaning “night.” The term nocturnal, meaning “of or related to the night,” also comes from this Latin root. In fact, English’s own word night is ultimately related to the Latin nox.

Also ultimately related to nox is the Greek for “night,” nýx, source of the combining forms nycto- and nyct-, which you can learn about at our Words That Use articles for the forms.

What are variants of nocti-?

When combined with words or word elements that begin with a vowel, nocti- becomes noct-, as in noctambulism.

Examples of nocti-

One example of a scientific term that features the combining form nocti- is noctilucent, a meteorological term for high-altitude clouds that are “visible during the short night of the summer.”

The first part of the word, nocti- means “night,” as we have seen. The -lucent part of the word means “shining” or “clear,” with a sense of “visible.” Noctilucent literally translates to “shining (at) night.”

What are some words that use or are related to the combining form nocti-?

What are some other forms that nocti- may be commonly confused with?

Break it down!

Noctiluca refers to a kind of marine plankton, also known as sea sparkle, that can produce light.

Given that the -luca part of the word means “shiner” and based on the meaning of nocti-, what does the name of this creature literally mean?

British Dictionary definitions for nocti-


before a vowel noct-

combining form


Word Origin for nocti-

from Latin nox, noct-
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