(a mass of) white or grey water vapour floating in the sky

mass of water particles in air

thin cloudy smoke or mist

cloudy air

the state of being hidden or unknown; something that is obscure

vagueness

a dark shape on the ground, a wall etc because of shade; to follow closely and watch the movements of (a person)

darkness

the faint light before sunrise or after sunset

onset of darkness at end of day