Many terms, practical and poetic, refer to various periods in the day or to related figurative senses. Here is a selection, ranging from regular to rare.
Dawn (from Old English dagian, “to become day”), a word for the beginning of the day, also figuratively describes beginnings in general, especially in the sense of renewal or second chances. Daybreak is a practical synonym.
A poetic variant is aurora, from the Latin name for the Roman goddess of dawn; the adjectival form is auroral. (The word is related to the Latin term auster, meaning “south wind,” from which the name of Australia is derived; the similar name Austria, by contrast, stems from the Germanic cognate of east, though auster and east are related.)
Aurora is usually associated with the aurora borealis and the lesser-known aurora australis, atmospheric phenomena occurring, respectively, in and near the Arctic and Antarctic regions. The name for Easter, derived from the name of a Germanic goddess, is associated with the brightness of dawn and is related to east.
Matutinal (from Matuta, an earlier Roman goddess later identified with Aurora) is an adjective referring to the morning; matins, the canonical term for the morning hours, and matinee, referring to an early performance, are related terms.
Twilight (from an Old English term probably meaning “half-light”) is the dim light of the early morning and late evening, as well as those times of the day, though the term almost invariably refers to the latter period. Figuratively, the word also refers to a vaguely defined intermediate state or a period of decline.
Gloaming (from Old English glom, meaning “twilight” — which, incidentally, is not related to gloom but is akin to glow, from glowan) declined in use in the eighteenth century except in certain dialects but is associated with Scotland and poetry because of its use by Scots poet Robert Burns and others.
Crepuscular (from Latin crepusculum, meaning “twilight, dusk”) is an adjective that refers to the margins of the day, especially in the evening, and might be used, for example, to refer to animal behavior. (Crepuscule and its variant crepuscle are rare noun forms.) Dusk (from Old English dox, and related to dun and dust) is the late evening twilight (and, rarely, the beginning of morning twilight); its adjectival form, dusky, refers to darkness or obscurity.
Terms for the beginning of the day other than dawn include sunrise and sunup, complemented by sunset and sundown; the archaic terms morn and eve survive as poetic alternatives to morning (from the Old English term morgen — the phrase to morgenne is the precursor of tomorrow) and evening (from even, in the sense of “equilibrium”). Other terms for morning include cockcrow, from the customary early-morning call of the rooster, while eventide and evenfall are poetic synonyms for evening.
Various terms derive from noon (ultimately from the Latin term nona hora, meaning “ninth hour,” though the sense shifted to “midday”): These include noontime, the poetic noontide, afternoon, and the rare forenoon.
Diurnal (from the Latin word diurnalis, also the precursor of journal), refers to daytime or daytime activity; the antonym is nocturnal (from the Latin term nocturnus).