Cabbage and lettuce are kind of similar but the difference between cabbage and lettuce is that Cabbage belongs to the Brassicaceae and the Cruciferae family whereas Lettuce belongs to the Asteraceae family.
Both Cabbage and Lettuce are leafy vegetables and are a great food to eat for health.
Another difference between cabbage and lettuce is that Cabbage has a short stem and a head, which has leaves gathered into a large bulb-like shape while lettuce doesn't.