As an adjective functional is

in good working order.

As a noun functional is

(mathematics) a function that takes a function as its argument; more precisely: a function y''=''f''(''x'') whose argument ''x varies in a space of (real valued, complex valued) functions and whose value belongs to a monodimensional space an example: the definite integration of integrable real functions in a real interval.

As verbs the difference between teach and enlighten

is that teach is to show (someone) the way; to guide, conduct while enlighten is to supply with light; to illuminate; as, the sun enlightens the earth.

As a noun teach

is teacher.

As a proper noun Teach

is nickname for a teacher.

As verbs the difference between affirm and validate

is that affirm is to agree, verify or concur; to answer positively while validate is to render valid.

As nouns the difference between service and diagnostic

is that service is service (eg in a restaurant) or service can be service, set while diagnostic is a technique etc used in medical diagnosis.

As an adjective diagnostic is

of, or relating to diagnosis.

As adjectives the difference between boorish and fractious

is that boorish is behaving as a boor; rough in manners; rude; uncultured while fractious is given to troublemaking.

As adjectives the difference between pervasive and thorough

is that pervasive is manifested throughout; pervading, permeating, penetrating or affecting everything while thorough is painstaking and careful not to miss or omit any detail.

As a preposition thorough is

(obsolete) through.

As a noun thorough is

(uk|dialect) a furrow between two ridges, to drain off the surface water.

As verbs the difference between organise and manage

is that organise is while manage is to direct or be in charge of.

As a noun manage is

the act of managing or controlling something.

As verbs the difference between execute and organise

is that execute is while organise is .

As a noun drum is

a percussive musical instrument spanned with a thin covering on at least one end for striking, forming an acoustic chamber, affecting what materials are used to make it.

As a verb drum is

to beat a drum.

As adjectives the difference between tacit and context

is that tacit is expressed in silence; implied, but not made explicit; silent while context is (obsolete) knit or woven together; close; firm.

As a noun context is

the surroundings, circumstances, environment, background or settings that determine, specify, or clarify the meaning of an event or other occurrence.

As a verb context is

(obsolete) to knit or bind together; to unite closely.