Tech & Science dictionary

civil twilight

[ siv-uhl twahy-lahyt ]

What is civil twilight?

Civil twilight is one of the technical divisions of twilight based on the angle of the sun in relation to the horizon and the resulting level of light in the sky. Civil twilight is the lightest (or least dark) of the three—when the sun is between 0 and 6 degrees below the horizon.

In general, the term twilight most commonly refers to the period after sunset before total darkness, but it can also refer to the period before sunrise. Civil twilight occurs in both cases—it is the time immediately before sunrise and the time immediately after sunset.

The exact timing and length of civil twilight varies by location and the time of year.

Two other divisions of twilight are called nautical twilight (when the sun is between 6 and 12 degrees) and astronomical twilight (often between 12 and 18 degrees).

These terms are typically used in technical and scientific contexts, including navigation, astronomy, meteorology, and related fields.

The term civil twilight is sometimes used more casually to refer to the time shortly after sunset when there is still some light in the sky (regardless of whether it is technically civil twilight). Still, in casual, nontechnical contexts, the term twilight is much more commonly used.

Example: In ideal conditions, some stars are bright enough to be observed during civil twilight.

Where does civil twilight come from?

sunset with cloudy sky, yellow filter

The term civil twilight is usually credited to scientist Johan Heinrich Lambert, who lived in the 1700s. The term has been commonly used since at least the mid-1800s.

The term civil twilight seems to use the word civil in its sense related to divisions of time, which suggests ordinary, civilian use in contrast with military or technical uses. (Nautical twilight is named in relation to the practical considerations of sailors and the name astronomical twilight references the time when most astronomical observations can begin.)

Examples of civil twilight

Late afternoon round of golf perfect walking weather civil twilight at 6:14. Beautiful sunset on the links.
@tomschwarm, January 6, 2011
Called the “Belt of Venus,” so-called because it’s around the same height as that planet is often seen at, it’s only visible during civil twilight.
Jamie Carter, Forbes, July 4, 2021

Who uses civil twilight?

Civil twilight is most commonly used in technical and scientific contexts, such as meteorology, astronomy, and navigation. Otherwise, in ordinary communication, most people simply use the word twilight or synonyms like dusk (at nighttime) or predawn (in the morning).

 

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Note

This is not meant to be a formal definition of civil twilight like most terms we define on Dictionary.com, but is rather an informal word summary that hopefully touches upon the key aspects of the meaning and usage of civil twilight that will help our users expand their word mastery.

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