Odorless means having no smell at all. Pure water is odorless: you can put your nose right up to a glass of it and smell nothing. Clean air is odorless too, though we rarely notice because we're so used to breathing it.

The word comes from odor (a smell) plus the suffix -less (meaning without). Many dangerous gases like carbon monoxide are odorless, which makes them particularly hazardous since people can't detect them without special equipment. That's why homes have carbon monoxide detectors: they alert families to an invisible, odorless threat.

Scientists prize odorless substances for experiments because smells can interfere with their work. A chemist testing how something tastes needs odorless containers so stray smells won't affect the results. Perfume makers start with odorless alcohol as a base, then add the fragrances they want.

When something is nearly odorless, it has such a faint smell that most people wouldn't notice it. Glass, most plastics, and refined metals are essentially odorless. The opposite would be pungent or fragrant, words for things with strong smells, whether pleasant or unpleasant.