Sufficient vs Necessary — Core Distinction

Sufficient condition: If this happens, the result is guaranteed. It's ENOUGH.

Necessary condition: This MUST happen for the result, but alone may not be enough.

Example: "Being a dog is sufficient to be an animal." (All dogs are animals.)

"Being an animal is necessary to be a dog." (You must be an animal to be a dog.)

On the LSAT:

"Sufficient assumption" questions: What one statement guarantees the conclusion?

"Necessary assumption" questions: What must be true for the argument to work?

The difference matters: A sufficient assumption is stronger — it proves the conclusion. A necessary assumption is weaker — without it the argument fails, but having it doesn't guarantee success.

Reference:

Wikipedia: Necessity and Sufficiency

https://en.wikipedia.org/wiki/Necessity_and_sufficiency