Any substance that has a distinctive smell, especially one added to something (such as household gas) for safety purposes

Having an odour/odor.

plural of odorant

odorous

Diffusing odour or scent; fragrant.

Any smell, whether fragrant or offensive. / (figuratively) A strong, pervasive quality. / (figuratively, uncountable) Esteem. / (now rare) Something which produces a scent; incense, a perfume.

plural of odor

Having a distinctive odor.

Having an odor, especially having a specified odor.

The addition of an odorant to a gas (so that leaks can be more easily detected)