focusing vs focussing

focusing and focussing both are nouns.

Word	Noun	Adjective	Verb	Adverb
focusing	Yes	No	No	No
focussing	Yes	No	No	No

As nouns, focusing and focussing are synonyms defined as:

focusing and focussing: the concentration of attention or energy on something

Other synonyms of focusing include centering, centring, direction, focal point, focus.

focusing (noun)	focussing (noun)
the act of bringing into focus	the concentration of attention or energy on something
the concentration of attention or energy on something