work vs fill

work and fill both are nouns.

Word	Noun	Adjective	Verb	Adverb
work	Yes	No	Yes	No
fill	Yes	No	Yes	No

As verbs, fill is a hyponym of work; that is, fill is a word with a more specific, narrower meaning than work:

work (noun)	fill (noun)
activity directed toward making or doing something	a quantity sufficient to satisfy
the occupation for which you are paid	any material that fills a space or container
a product produced or accomplished through the effort or activity or agency of a person or thing
a place where work is done
the total output of a writer or artist (or a substantial part of it)
applying the mind to learning and understanding a subject (especially by reading)
(physics) a manifestation of energy; the transfer of energy from one physical system to another expressed as the product of a force and the distance through which it moves a body in the direction of that force

work (verb)	fill (verb)
give a workout to	become full
arrive at a certain condition through repeated motion	make full, also in a metaphorical sense
go sour or spoil	plug with a substance
cause to undergo fermentation	fill to satisfaction
find the solution to (a problem or question) or understand the meaning of	eat until one is sated
use or manipulate to one's advantage	fill, satisfy or meet a want or need or condition or restriction
to mix into a homogeneous mass	assume, as of positions or roles
perform as expected when applied	appoint someone to (a position or a job)
move into or onto	occupy the whole of
shape, form, or improve a material
cause to happen or to occur as a consequence
prepare for crops
make something, usually for a specific function
gratify and charm, usually in order to influence
proceed along a path
move in an agitated manner
provoke or excite
be employed
cause to work
exert oneself by doing mental or physical work for a purpose or out of necessity; work
have an effect or outcome; often the one desired or expected
operate in a certain place, area, or specialty
proceed towards a goal or along a path or through an activity
have and exert influence or effect
operate in or through
cause to operate or function
behave in a certain way when handled