focal vs central

focal is not a noun while central is a noun.

Word	Noun	Adjective	Verb	Adverb
focal	No	Yes	No	No
central	Yes	Yes	No	No

focal (noun)	central (noun)
	a workplace that serves as a telecommunications facility where lines from telephones can be connected together to permit communication

focal (adjective)	central (adjective)
of or relating to a focus	in or near a center or constituting a center; the inner area
having or localized centrally at a focus	serving as an essential component