center of curvature vs centre of curvature

center of curvature and centre of curvature both are nouns.

Word	Noun	Adjective	Verb	Adverb
center of curvature	Yes	No	No	No
centre of curvature	Yes	No	No	No

As nouns, center of curvature and centre of curvature are synonyms defined as:

center of curvature and centre of curvature: the center of the circle of curvature

center of curvature (noun)	centre of curvature (noun)
the center of the circle of curvature	the center of the circle of curvature