diadem

As nouns the difference between circle and diadem

is that circle is (lb) a two-dimensional geometric figure, a line, consisting of the set of all those points in a plane that are equally distant from another point while diadem is an ornamental headband worn as a badge of royalty.

As verbs the difference between circle and diadem

is that circle is to travel around along a curved path while diadem is to adorn with a diadem; to crown.

As nouns the difference between bandeau and diadem

is that bandeau is a band for the hair while diadem is an ornamental headband worn as a badge of royalty.

As a verb diadem is

to adorn with a diadem; to crown.

As nouns the difference between diadem and tiar

is that diadem is an ornamental headband worn as a badge of royalty while tiar is (poetic|archaic) a tiara.

As a verb diadem

is to adorn with a diadem; to crown.

As nouns the difference between diadem and circlet

is that diadem is an ornamental headband worn as a badge of royalty while circlet is a small circle.

As a verb diadem

is to adorn with a diadem; to crown.

As nouns the difference between diadem and diadumenos

is that diadem is an ornamental headband worn as a badge of royalty while diadumenos is a form of ancient greek sculpture featuring a young man holding a knotted diadem (as the winner of a contest).

As a verb diadem

is to adorn with a diadem; to crown.