Odds
Etymology
English from the 16th century, of disputed origin; most likely the plural of “odd” in its older sense of inequality or an uneven amount, the notion being the unequal stakes between two parties. The precise route is uncertain and etymologists flag it as unresolved.
noun · /ODZ/
A way of stating chance as the ratio of an event happening to it not happening, such as 3-to-1.
What it names
It captures how betting, medicine, and everyday speech actually quote risk — by comparison rather than by share of the whole.
Example
Saying a horse is “5-to-1” means bookmakers judge it will lose five times for every one time it wins — an implied probability of about one in six.
Related idea
Odds and probability describe the same uncertainty but with different denominators, so “the odds doubled” and “the probability doubled” are not interchangeable claims — a subtlety that trips up health-risk headlines constantly.