Germane (adj.): Closely related, connected, or relevant to the current topic or situation.
Courtesy of Oxford Dictionary Online
This could easily just be me, but I was largely unaware of this word until about two weeks ago when I read it somewhere and realized I'd never really encountered it before. This is a good example of how even relatively well-read people have plenty of opportunities to continue to expand their vocabulary.
As a fun aside, this definition arose from its use in Shakespeare's Hamlet, Act V, scene ii: "The phrase would be more germane to the matter if we could carry a cannon by our sides; I would it might be hangers till then."