Citation:
Monolid, referring to eyelids that do not have a visible crease.
Double eyelids, where there is a visible crease on the eyelid.
内双眼皮（nèi shuāng yǎnpí）: Inner double eyelids, where the crease is closer to the inner corner of the eye.
外双眼皮（wài shuāng yǎnpí）: Outer double eyelids, where the crease is closer to the outer corner of the eye.