The old motorcycle stalled halfway up the hill because of a vapour lock.

In the lab, we measured the vapour density of the unknown gas to determine its relative molecular weight compared to hydrogen.

We watched the airplane carve a thin vapour trail across the clear blue sky.

We lay on the grass and watched the vapour trails drift lazily across the blue sky.

Street workers replaced the old sodium vapour lamp to reduce the orange glare and improve visibility at night.

The meteorologist calculated the saturation vapour pressure to determine how much moisture the air could hold.

The old mercury-vapour lamp in the factory cast a cold, bluish light that made the whole room feel sterile.

The old factory yard was dimly lit by several mercury-vapour lamps that hummed faintly overhead.

Measurements of saturation vapour pressures at different temperatures are essential for accurate humidity modelling.