unless

I shall not go unless the weather is fine.

Definition

1. Conjunction:
   • Except if; on a condition other than if: "unless" introduces a condition that must be met for the main clause to be true or to happen; it is equivalent to "if not" or "except when."
   • Used to express an exception: It indicates that the stated outcome will occur only if the following condition is not fulfilled.

Usage Examples

• (I will go only if the weather is fine; otherwise, I will not go.)
• (If you do not try, you will never succeed.)
• (The meeting can begin only after everyone arrives; if someone is absent, it will not start.)

Advanced Usage

• "unless and until": A emphatic or formal phrase meaning "except if and up to the time when."
  • The contract is not valid unless and until both parties sign it. (The contract has no effect except after both parties have signed it.)
• "unless otherwise": Used in legal or formal contexts to indicate a default rule unless a different condition is specified.
  • Unless otherwise stated, all prices include tax. (If no other statement is made, the prices include tax.)

Variants and Related Words

• Un- (prefix): The word "unless" historically combines "on" (as in "on less than") and is not a productive prefix in modern English; no direct variants exist.
• Unless (adverb, rare): Occasionally used as an adverb in informal speech, though this is nonstandard.
  • I'll be there at 6, unless. (Meaning: I'll be there at 6, except if something prevents me; this usage is very informal and usually avoided in writing.)

Synonyms

• If not: a direct synonym that reverses the condition.
  • You will fail if you don't study. (Equivalent to "You will fail unless you study.")
• Except if: a more formal synonym.
  • We'll go except if it rains. (We'll go only if it does not rain.)

Related Idioms

• Unless I'm mistaken: a phrase used to express a tentative belief or assumption.
  • Unless I'm mistaken, the train arrives at 3 p.m. (I believe the train arrives at 3 p.m., but I may be wrong.)
• Unless the cows come home: a humorous, informal idiom meaning "for a very long time" or "indefinitely."
  • We could argue about this unless the cows come home. (We could argue about this forever, without resolution.)