What is the lightest vegetable?

This is a tricky question! "Lightest" can refer to two things:

* Weight: In terms of weight per unit volume, lettuce is a very light vegetable. It's mostly water, making it very low in density.

* Calorie Content: If you're looking for the lowest calorie vegetable, cucumber is a strong contender. It's very low in calories and high in water content.

So, depending on your definition of "lightest," the answer could be either lettuce or cucumber.