Dome

The dome was the top part or "head" of a Dalek's casing, upon which the eyepiece was mounted. At GeoComTex, the Ninth Doctor instructed security personnel to aim for the "Metaltron's" dome, specifically the eyepiece. (TV: Dalek)

The Emperor's Personal Guard were distinguished by their black domes. (TV: The Evil of the Daleks, The Parting of the Ways)

During the Last Great Time War, members of the Dalek Scientific Division were distinguished by their blue domes. (AUDIO: A Thing of Guile)