Noun
A noun is a person, place or thing, though preferably — in the mind of a quill-wielding solicitor — an abstract thing that started out life as a verb.
As far as your counsel is concerned, the best kinds of nouns have gone through several grammar reassignment operations: That old favourite applicability started out life as a verb (“apply”), became a noun (“application”), reverted back to a verb — albeit a passive one — (“to be applicable”), and eventually settled on a life of tedious nounitude in its adult form as “applicability”.