limbus
/ˈlɪmbəs/noun
(pl. limbi /-baɪ/)
- Anatomy the border or margin of a structure, especially the junction of the cornea and sclera in the eye【剖】（尤指角膜和巩膜连接处的）缘。
词源
late Middle English (denoting limbo)： from Latin， 'edge， border'. The current sense dates from the late 17th cent.