vapour, vaporize, vaporous

In such words as vapour, Canadians generally prefer the British ending ‑our to the American variant ‑or.

• A microwave radiometer measures atmospheric water vapour.

However, the u is dropped in vaporize and vaporous.

• The doctor used a laser to vaporize the patient’s urinary tract stones.
• On hot days the children liked to play under the vaporous spray of the fountain.