The odds are the likelihood of something happening. The odds are against it, what are the odds, beat the odds.
It is always plural in this sense. In betting, odds have a precise form — five to one, evens — and they express the payout as much as the probability. Two idioms are very common: against all odds, meaning despite everything, and odds and ends, meaning small leftover items, which is a completely separate use. Note at odds with, meaning in disagreement or conflict with, which is formal and appears constantly in reporting.
1nounoddsThe likelihood of something happening.
“The odds of that happening twice are remarkable.”
2nounratioThe ratio a bookmaker pays on a bet.
“The odds shortened the week before the race.”
Too few real examples of this word to estimate which sense is commonest.
odds is a measure of likelihood.
Odds come from odd, meaning uneven. The odds on a bet are a measure of how far the two sides fail to match.
Built from
From odd (“uneven, strange”).
Etymology from Wiktionary, CC BY-SA