Traditionally, mopeds were based on the design of a motorcycle but had the addition of pedals, the name being a portmanteau of 'mo'torcycle and 'ped'al. While the design feature fell out of favour, the name stuck and is now used legally to refer to any low-powered motorcycle with a capacity of less than 50cc. Mopeds tend to resemble the bikes they were based on, while scooters feature a step-through frame. Some scooters have capacities of less than 50cc, meaning they're legally mopeds, but they are also available in more powerful capacities.