ra·mus 
(rāməs)
(rāməs)n. pl. ra·mi (-mī′)
1. A branch, as of a nerve or blood vessel, or a projecting part, as of a rotifer or crustacean.
2. A bony process extending like a branch from a larger bone, especially the ascending part of the lower jaw that makes a joint at the temple.
[Latin rāmus, branch; see wrād- in the Appendix of Indo-European roots.]