Worse compares one thing with another: "Today was worse than yesterday." Worst marks the bottom of an entire group: "That was the worst day of the year." If the word is followed by than, use worse; if it is preceded by the, use worst.
Bad has an irregular set of forms: bad, worse, worst. Worse is the comparative — it sets two things against each other. Worst is the superlative — it picks out the lowest of everything under discussion.
The same logic governs good, better, best; the only reason worse and worst cause more trouble is that they differ by a single letter and sound alike in fast speech.
How to use worse
- "The second album is worse than the first."
- "His cough got worse overnight."
- "Things could be worse."
- "Worse still, the backup had failed too."
How to use worst
- "It's the worst film I've ever sat through."
- "He came worst in the qualifying round."
- "At worst, we lose a day's work."
- "The worst of the flooding was in the north."
The test
Two quick checks, either of which settles it:
- If than follows, or could follow, use worse. "Worse than last time."
- If the comes before it, use worst. "The worst outcome."
A third check for the ear: worse pairs with better, worst pairs with best. Say the sentence with the positive version. If "better than" would fit, you want worse. If "the best" would fit, you want worst.
Where people slip
The most frequent error is "one of the worse things" for "one of the worst things". The phrase "one of the..." always calls for a superlative, because it selects from a group.
Another is "worse case scenario", which should be worst-case scenario — it means the very worst of all possible cases, not a comparison between two. Write it hyphenated when it sits before a noun: "a worst-case estimate".
Watch also for the fixed phrases, which are not interchangeable. "If worse comes to worst" and its American variant "if worst comes to worst" both circulate and both are accepted; either is fine, but do not mix them into "if worst comes to worse".
Finally, worse is not a verb. To make something worse is to worsen: "The delay worsened an already difficult situation."
Frequently Asked Questions
Is it "worse case scenario" or "worst case scenario"?
"Worst-case scenario." It means the most severe of all possible outcomes, so it needs the superlative. Hyphenate it before a noun.
Is it "one of the worse" or "one of the worst"?
"One of the worst." Any phrase beginning "one of the" is selecting from a whole group, which calls for the superlative form.
Which is right: "if worse comes to worst" or "if worst comes to worst"?
Both are established and both are accepted. The first is older and commoner in British English; the second is common in American English. Just avoid mixing them.