Stock refers to a moped or moped part that is in a configuration as it came from the factory.

Stock mopeds do not have any aftermarket upgrades or modifications. They do not necessarily have to be in mint condition, or look brand-new. Many would consider an older bike with replacement stock parts to still be "stock".

Stock parts are parts that are identical to the original ones found on a particular moped. Again, these parts may or may not be in good shape and they may be New old stock or reproductions.