1) Chemical nomenclature 
In chemistry, the term geminal refers to the relationship between two atoms or functional groups that are attached to the same atom. The word comes from Latin gemini meaning `twins`. A geminal diol, for example, is a diol (a molecule that has two alcohol functional groups) attached to the same carbon atom, as in methanediol. The prefix gem may a.....
• (a.) A pair.
Gem'i·nal adjective [ Latin geminus twin.] A pair. [ Obsolete] Drayton.