Happening in the evening or at night-fall, vespertine, as the acronychal rising or setting of a star.

By night; nightly.

An old medical term that refers to the eruption that affects the skin on the arms, hands, and thighs only at night.

Orientation movements in plants during darkness in response to gravity; geonyctitropic.

Pain that occurs only during sleep at night or any recurrent nocturnal pain..

1. Night blindness; failure or imperfection of vision at night or in a dim light. Smoking tobacco may impair the ability to see at night. Hypoxia associated with being above sea level in an aircraft will also decrease night vision.
2. The inability to see well under scotopic (dark) conditions, due to faulty rod function. The “rod” used here refers to any of the photoreceptor cells of the retina serving scotopic vision. “Scotopic vision” designates the dark-adapted state of vision, in which color perception is replaced by shades of black and white. It is served by the rod photorecptors.
3. A condition of the eyes in which the person can see well during the day, in a strong light, or on bright days, but see poorly at night, in a faint light, or on dull or dark days; night blindness; day sight.
4. The opposite of nyctalopia is hermeralopia, or day blindness.

Reduction or dimness of vision at night without visible eye changes.

Flowering only during the night.

An elective mutism indicating the loss of one’s voice during the night.

Someone who hunts by night.

Nocturnal; or pertaining to night, especially to a night-time period of animal activity.

Of or relating to the alternation of day and night, particularly a single night followed by day; a full period of nigh and day.

A reference to flowers that open at night and close during the day; nygtigamy.

A genus of bioluminescent marine organisms that, when grouped in large numbers, make the seas phosphorescent.

Orientation movements of plants during the night; nyctinastism. Nastic movements of plant organs in response to the changes in light and temperature that occur between day and night (and vice versa). Examples are the opening and closing of many flowers and the folding together of the leaflets of clover and other plants at night.

1. Pertaining to organisms that migrate into the upper surface waters at night.
2. Bathypelagic and appearing at the surface only at night. Bathypelagic refers to creatures that live in deep water below the level of light penetration, between 1,000 meters and 4,000 meters deep.

A period of darkness; a dark phase in a light/dark cycle.

An orientation response occurring at night or turning in a certain direction at night; nyctitropic, nyctitropism. The tendency of certain plant organs, as the leaflets of clover, to assume special “sleeping” positions at night.

A device invented by Lewis Carroll with which one can record one’s ideas at night, in the dark, or when not fully awake.

Night blindness; failure or imperfection of vision at night or in a dim light, with good vision only on bright days.

1. In biology, a preference for the dark or for night.
2. An abnormal preference for darkness or night.

A person who has an abnormal preference for darkness or night.

Someone who has an irrational fear of the dark.

An irrational fear of the dark.

An elective mutism with the loss of one’s voice during the day but not at night.

The inability to see well at night.

1. Frequent urination during the night; especially, the passage of more urine at night than during the day; nocturia.

The Greek goddess of night, known to the Romans as Nox, was born, together with Erebus (Darkness), Ge (Earth), Tartarus, and Eros (Love), out of Chaos. With Erebus, she bore Aether (Upper Air) and Hemera (Day). She alone spawned a large brood that included Moros (Doom), Thanatos (Death), Hypnos (Sleep), the Fates, and Nemesis.

Nyx lived in Tartarus, from which she went forth each day just as Hemera was returning. Her only other recorded act was to save her son Hypnos when Zeus was about to throw him out of the realm of the gods. Tartarus, by the way, was a dark region beneath the earth, and the personification of that region. Tartarus was said to be as far beneath Hades, or beneath the surface of the earth, as heaven was above it. Supposedly, an anvil would fall for nine days to reach it from earth’s surface.