Definition of a kiss

Prof. of Economics
Kiss is that thing for which the demand is always higher than the
supply.

Prof. of Accountancy
Kiss is a credit because it is profitable when returned.

Prof. of Algebra
Kiss is infinity because two divided by nothing.

Prof. of Geometry
Kiss is the shortest distance between two lips.

Prof. of Physics
Kiss is the contraction of mouth due to the expansion of the heart.

Prof. of Chemistry
Kiss is the reaction of the interaction between two hearts.

Prof. of Physiology
Kiss is the juxtaposition of two orbicularisoris muscles in the state
of contraction.

Prof. of Dentistry
Kiss is infectious and antiseptic.

Prof. of Philosophy
Kiss is the persecution for the child, ecstasy for the youth and homage for the old.

Prof. of Comp.Science
What is a kiss? It seems to be an undefined variable!

Prof. of English
Kiss is a noun that is used as a conjunction, it is more common than
proper, it is spoken in the plural