A leak is an escape, whether of water, gas or secret information. A leek is a vegetable. Memory hook: leek has a double e, like the two e's in green and tree, and leeks are green.
The core difference
Leak is about something escaping; leek is a mild vegetable related to the onion.
- leak — a hole or escape, or to let something escape: There is a leak under the kitchen sink.
- leek — a long, mild vegetable: She added chopped leeks to the potato soup.
How to tell them apart
Both words are pronounced the same, so it comes down to meaning. If something is dripping, escaping or being revealed without permission, write leak. If you can chop it and put it in a pot, write leek.
The slip happens most in news headlines about a leak of information, and in recipes where leek is typed as leak. A handy trick: ee in leek looks like two stalks standing side by side.