CONCENTRIC is a 10 letter word that starts with C.

1. \Con*cen"tric\, Concentrical \Con*cen"tric*al\, a.
   [F. concentrique. See {Concenter}.]
   Having a common center, as circles of different size, one
   within another.
   
         Concentric circles upon the surface of the water. --Sir
                                                  I. Newton.
   
         Concentrical rings like those of an onion. --Arbuthnot.
   
   

2. \Con*cen"tric\, n.
   That which has a common center with something else.
   
         Its pecular relations to its concentrics. --Coleridge.