ru·by 
(rbē)
(rbē)n. pl. ru·bies
1. A red, translucent variety of the mineral corundum, highly valued as a precious stone.
2. Something, such as a watch bearing, that is made from a ruby.
3. A dark or deep red to deep purplish red.
adj.
Of the color ruby.
[Middle English, from Old French rubi, from Medieval Latin rubīnus (lapis), red (stone), ruby, from Latin rubeus, red; see reudh- in the Appendix of Indo-European roots.]