center of gravity vs centre of gravity

center of gravity and centre of gravity both are nouns.

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

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

center of gravity and centre of gravity: the point within something at which gravity can be considered to act; in uniform gravity it is equal to the center of mass

center of gravity (noun)	centre of gravity (noun)
the point within something at which gravity can be considered to act; in uniform gravity it is equal to the center of mass	the point within something at which gravity can be considered to act; in uniform gravity it is equal to the center of mass