Lettuce is a temperate annual or biennial plant most often grown as a leaf vegetable. In some countries, it is typically eaten cold and raw, in salads, hamburgers, tacos, and many other dishes. In some places, including China, lettuce is typically eaten cooked and use of the stem is as important as use of the leaf.
The Lettuce plant has a short stem initially (a rosette growth habit), but when it blooms the stem lengthens and branches, and it produces many flower heads that look like those of dandelions, but smaller. This is called bolting. When grown to eat, lettuce is harvested before it bolts.
In many parts of the southern tier of New York, people eat lettuce leaves with ketchup as a snack in a style similar to chips and dip. Lettuce is used as a food plant by the larvae of some Lepidoptera.
Both the English name and the Latin name of the genus are derived from lactis, the Latin word for "milk", referring to its milky juice of the plant.