I know that's "sorta" two questions in one, but I'm stuck in an argument with a guy who says both words can apply to morning half-light. I disagree and think both only apply in the evening.

I think both can only be used about dim light in the evening, but I have to admit I don't know any equivalent words for dim light in the morning.

EDIT: More votes needed! I get the feeling I'm losing here!

  • Great question--led me to discover a bunch of new words. Jun 2 '12 at 21:52
  • 2
    'Crepuscular', as a technical biological term, refers to the 'shoulder' times, both dusk and dawn, neither complete night nor full day. 'Twilight' I've always held to be both dusk and dawn. Is 'dawn' what you're looking for for just the morning? (where 'dusk' is -just- the evening dimness)
    – Mitch
    Jun 3 '12 at 15:19
  • To the average person, "twilight" is taken to mean a time in the day when the sun is near the horizon. This is witnessed more often in the evening than in the morning, of course, simply because most people don't get up before dawn (or if they do they're too bleary-eyed to observe it). "Crepuscular", on the other hand, would be taken by most to refer to some sort of French pastry.
    – Hot Licks
    Jul 20 '15 at 16:36
  • I was gonna make a vampire joke, but it really sucked.
    – Patrick M
    Jul 20 '15 at 18:35

Sorry, FF, but twilight is well defined as a technical term strictly relating to degrees of solar elevation. In other words equally as applicable to near sunrise as to near sunset. And if anything, crepuscular refers more likely to morning twilight than it does evening, though it more formally means both.

  • 1
    Yeah, I think you're right. My guess is that most usages of "twilight" do in fact refer to the evening, simply because that's the one we're more likely to be talking about. But it does seem indisputable that the word itself is equally applicable to both. And I now see that whilst OED says crepuscular = twilit" (i.e., both morning *and evening), it has a separate definition explicitly saying particularly of morning twilight. I was mistaken, and have conceded the argument that led me to pose this question (thanks for nothing, guys! ;) Jun 3 '12 at 19:18
  • @tchrist: Old Pro's Wikipedia link, which I feel unable to take issue with, starts by saying "Twilight is the time between dawn and sunrise or between sunset and dusk". So OldPro is quite correct to say "In other words morning and evening", even if you don't buy into the final comment re crepuscular (I'm still a little uncertain about that myself). Jun 3 '12 at 19:21
  • @FumbleFingers I take issue with his saying that twilight “means” morning and evening, rather than saying that it occurs during both of those periods. In re crepuscular, the Latin had it as a diminuitive of evening, but there are historical uses related to the morning. Those are all OED2 cites, so check your copy for which years had the morning version.
    – tchrist
    Jun 3 '12 at 19:22
  • @tchrist: oic. Well I think that was a minor detail, since in context it's clear what was meant. Anyway, as I write I see it's been changed, so here comes my acceptance. No disrespect, but your answer is a bit lengthy for my question as posed, even if it suits others who want a more in-depth analysis. Jun 3 '12 at 19:26
  • @FumbleFingers I don’t care whose answer you accept, I just wanted to get the info out there. I do think that twilight, crepuscule, and gloaming can all three of them be applicable to both the dawn version and the dusk version, even if earlier writers sometimes limited it to one or the other end. Certainly biologists use crepuscular to mean both times. More people are awake for the evening twilight than for the morning one, so that may account for more uses being about then. I also like the connection between gloom and gloaming.
    – tchrist
    Jun 3 '12 at 19:30

Twilight can apply to morning or evening. Etymology is confused, it seems, but twi- either means "half-" or "two". That is, it's either half-light or a light which occurs twice a day. Either way, it's morning and evening.

Crepuscular is more interesting. Etymonline says both and particularly morning:

crepuscular fig. use from 1660s; lit. use from 1755, from L. crepusculum "twilight." Especially of morning twilight.

Collins nearly agrees:

crepuscular (krɪˈpʌskjʊlə) — adj
1. of or like twilight; dim
2. (of certain insects, birds, and other animals) active at twilight or just before dawn
[C17: from Latin crepusculum dusk, from creper dark]

...but implies that "twilight" isn't "just before dawn", and translates crepusculum as dusk, which is definitely evening twilight.

I had always thought crepuscular was related to dusk rather than dawn, but I'd be stumped to find another accepted word to describe animals active in morning twilight! Matutinal could mean "of the dawn" but is more likely simply to mean "of the morning" and auroral is more likely to be associated with polar aurorae.

It does look like your protagonist is right.

  • 1
    Usage note: COCA morning twilight 51, evening twilight 71. Ngrams: books.google.com/ngrams/…
    – z7sg Ѫ
    Jun 2 '12 at 20:33
  • @Andrew, the Collins definition does not imply that "twilight" is not just before dawn. Rather, it allows for insects which are only active just before dawn to be considered crepuscular even though they are not active around dusk.
    – Old Pro
    Jun 3 '12 at 18:42
  • @OldPro Yes I just realised that that "or" could be read as "in other words". Hmm...
    – Andrew Leach
    Jun 3 '12 at 18:51
  • @z7sg Ѫ: On the other hand, with default daterange 1700-2000, NGrams claims 8.3M instances of the word twilight itself, of which 114K (about 60%) are evening twilight, and 84K are morning twilight. I suspect that far more than 60% of those "bare" instances do in fact specifically refer to the evening - which doesn't need to be qualified as such because it's the default assumption. Jun 3 '12 at 18:51
  • @FumbleFingers It's certainly the commoner twilight but perhaps that's only because it's the one we most experience. I usually sleep through the morning twilight.
    – z7sg Ѫ
    Jun 3 '12 at 20:04

Some basic definitions:

crepuscular, adj. : active in the twilight

twilight, n. : the light from the sky between full night and sunrise or between sunset and full night

So crepuscular absolutely applies to the periods before sunrise or after sunset when it's not full night.

Note also this article:

When an animal is said to be crepuscular, it is active during the twilight hours at dawn and dusk... Rabbits and cats are both famously crepuscular.


I found this University of Illinois source that mentions both "morning twilight" and "evening twilight." So, I would say that it can be used accurately for both the time between evening and full dark and full dark and dawn. This source is very specific about when twilight ends in the evening: "Perfect darkness is achieved when the Sun sinks to 18 degrees below the horizon, at which time no light reaches even the upper air, and twilight is over."

That being said, I think most people think of twilight as being after the day, before full darkness sets in. I personally would use dawn for the morning light.

As for crepuscular, this article makes a further distinction:

Special classes of crepuscular behaviour include matutinal (or "matinal") and vespertine, denoting species active only in the dawn or only in the dusk, respectively. Those that are active mainly during both morning and evening twilight are said to have a bimodal activity pattern. (emphasis mine)

  • The US Naval Observatory has definitions of several grades of twilight, based on the sun's position below the horizon. Their definitions agree with your source's 18° limit on twilight, but explicitly include both morning and evening.
    – Simon
    Jun 4 '12 at 16:40
  • EDIT: You left out the related gloaming, now included below. All three of these terms — twilight, crepuscule, and gloaming — seem usable for either half-light period, although during some historical periods occasionally one or the other of the two ends of that was the more common. Old English had a disambiguating variant, ǽfen-glommung, as today we might use evening twilight. Personally, I find dawn and dusk the simplest and most direct of all these, although perhaps twilight places an emphasis on the lighting.

The answer is that both crepuscular and twilight refer to the the half-darkness of the dawn (that is, before sunrise) and of the dusk (that is, after sunset). Neither is more of one nor the other, at least in modern use. I’m most familiar with characterizing felines as crepuscular critters, where no bias towards the morning nor towards the evening is either meant or implied.

The OED gives perhaps a more complete view of these, including several similar words with the same ultimate ancestry and which entered English nearabouts the same time as crepuscular did. Citations omitted for the sake of brevity.

twilight n. [1412–20]

    • a. Generally.
    • b. spec. Most commonly applied to the evening twilight, from sunset to dark night. second twilight n. see quot. 1883.
    • c. Morning twilight, which lasts from daybreak to sunrise.
  1. transf. A dim light resembling twilight; partial illumination.
  2. fig.
    • a. An intermediate condition or period; a condition before or after full development.
      twilight of the gods [transl. of Icelandic ragna rökkr, altered from the original ragna rök, the history or judgement of the gods], in Scandinavian Mythol. the destruction of the gods and of the world in conflict with the powers of evil; also transf. Cf. Götterdämmerung n., Ragnarök n.
    • b. esp. in reference to imperfect mental illumination or perception.
    • a. Of, pertaining to, or resembling twilight; seen or done in the twilight.
      twilight arc (also twilight arch), twilight curve, the outline of the earth's shadow, which rises in the east as the sun sets, forming an arch which divides the twilight or shaded portion of the sky from that which is lighted by the direct rays of the sun. twilight glow, a diffuse glow in the sky at twilight; spec. in Meteorol., that caused by spectroscopic emission in the upper atmosphere from atoms excited by solar radiation. twilight parallel, the small circle of the celestial sphere, parallel to and 18 degrees below the horizon, at the sun's crossing which evening twilight ceases or morning twilight begins (Webster, 1911). twilight vision, vision in which colours are hardly perceptible owing to the dimness of the light; scotopic vision.
    • b. fig. Having an intermediate character.
    • c. Lighted as by twilight; dim, obscure, shadowy; also fig. of early times.
    • d. fig. Of the nature of or pertaining to imperfect mental light.

The etymology provided for twilight is:

Middle English, < twi- comb. form + light , corresponding to West Frisian twieljocht, Dutch tweelicht (from 16th cent.), Low German twilecht, German zwielicht. The rare form twilighting n. is recorded a little earlier. The exact force of twi- here is doubtful: compare in same sense Middle High German zwischenliecht ‘'tweenlight’, and Low German twêdustern, twêdunkern, lit. ‘twi-dark’.

And here are the various crepusc- headwords:

crepuscle n. [1665]


crepuscular adj. [1668]

  1. Of or pertaining to twilight.
    • a. fig. Resembling or likened to twilight; dim, indistinct.
    • b. esp. Resembling or likened to the morning twilight as preceding the full light of day; characterized by (as yet) imperfect enlightenment.
  2. Zool. Appearing or active in the twilight.

crepuscule n. [c1400]

Now rare.

crepusculine, adj. and n. [c1550]

A. adj Pertaining to twilight; illuminated by twilight, dim, dusky.
†B. n. The (morning) twilight. Obs.

crepusculous, adj. [1646]

Of the nature of twilight; dim, dusky, indistinct. (lit. and fig.)

crepusculum, n. [1398]

Twilight, dusk.

The etymology given for the very last of those, which is clearly both the earliest and the least assimilated into English, is:

Latin = twilight, a diminutive formation, related to creper dusky, dark, creperum darkness.

Here is the entry for gloaming. This time I will give its citations, because they include mentions of the two preceding terms.

gloaming, n. [c1000]

Pronunciation: /ˈgləʊmɪŋ/
Forms: OE glómung, (ǽfen-)glommung, ME glomyng, ME–16 gloming, 17– gloaming.
Etymology: repr. Old English glómung strong feminine, < (on the analogy of ǽfning evening n.¹) glóm twilight, probably < the Germanic root ∗glô- (see glow n.); the etymological sense would thus seem to be the ‘glow’ of sunset or sunrise (compare gloom n.²), whence the passage to the recorded sense is not difficult.

The vowel of the mod. gloaming is anomalous, as Old English glómung should normally become glooming. The explanation probably is that the ó was shortened in the compound ǽfen-glommung (as the spelling seems to show was actually the case), and that from this compound there was evolved a new n. glŏmung, which by normal phonetic development became Middle English glǭming, modern English gloaming. In the literary language the word is a comparatively recent adoption from Scottish writers; but it is found in the dialect of Mid. Yorks.

  • a. Evening twilight.

    • c1000 in T. Wright & R. P. Wülcker Anglo-Saxon & Old Eng. Vocab. (1884) I. 117/7 Crepusculum, glomung.
    • c1000 in J. Stevenson Lat. Hymns Anglo-Saxon Church (1851) 16 Crepusculum mens nesciat, æfen glommunge mod nyte.
    • c1425 Wyntoun Cron. ɪᴠ. vii. 827 Fra the glomyng off the nycht.
    • c1540 J. Bellenden tr. H. Boece Hyst. & Cron. Scotl. ɪx. xxv. f. 128ᵛ/2, He‥efter supper past furth in yᵉ glomyng.
    • c1610 in R. Pitcairn Criminal Trials Scotl. III. 3 This fell furth in the gloming.
    • 1786 R. Burns Twa Dogs xxxv, in Poems 21 By this, the sun was out o' sight, An' darker gloamin brought the night.
    • c1800 Hogg Song, 'Tween the gloaming and the mirk, When the kye comes hame.
    • 1807 Byron Elegy Newstead Abbey ix, Soon as the gloaming spreads her waving shade.
    • 1830 Tennyson Leonine Elegiacs, Lowflowing breezes are roaming the broad valley dimmed in the gloaming.
    • 1866 ‘G. Eliot’ Felix Holt I. Introd. 2 The happy outside passenger seated on the box from the dawn to the gloaming [etc.].
    • 1786 R. Burns Poems 73 When ance life's day draws near the gloamin.
    • 1889 J. M. Barrie Window in Thrums xvi. 144 The help she and Hendry needed in the gloaming of their lives.
  • b. Said occas. of morning twilight.

    • 1873 H. B. Tristram Land of Moab iii. 38 The sun had scarcely cast the gloaming of approaching dawn over the eastern peaks.
    • 1894 S. R. Crockett Raiders 21, I rowed home in the gloaming of the morning.
  • c. Shade, dusky light.

    • 1832 W. Motherwell Jeanie Morrison vii, And in the gloamin o' the wood, The throssil whusslit sweet.

So it seems that gloaming is more often the evening twilight of dusk, but sometimes the morning twilight of dawn. Amongst its compounds are a gloaming sight, a special kind of sight used for shooting guns and rifles in the evening hours.


There are some interesting terms that have relevance here. One is matutinal, which Wordnik defines as "of, relating to, or occurring in the morning; early." Wikipedia is more specific: "a term used in the life sciences to describe an organism that is only or primarily active in the pre-dawn hours or early morning." Here's an example in the form of a scholarly paper: "By Dawn's Early Light: Matutinal Mating and Sex Attractants in a Neotropical Mantid."

Another terms is matinal, which Wordnik defines as "relating to the morning, or to matins." The Wikipedia reference to matutinal says that matinal is a variant term "used only in entomology, often used in literature on the natural history and ecology of bees." In a church-related note, Wikipedia defines vespertine as "a term used in the life sciences to indicate something of, relating to, or occurring in the evening." Flowers that bloom only in the evening are an example.


An interesting word that seems only to have the evening twilight sense is the dialectical dimmet, defined here as "twilight" or "dusk".

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