substance vs viscosity

substance and viscosity both are nouns.

Word	Noun	Adjective	Verb	Adverb
substance	Yes	No	No	No
viscosity	Yes	No	No	No

As nouns, viscosity is a hyponym of substance; that is, viscosity is a word with a more specific, narrower meaning than substance:

substance (noun)	viscosity (noun)
the real physical matter of which a person or thing consists	resistance of a liquid to shear forces (and hence to flow)
a particular kind or species of matter with uniform properties
the property of holding together and retaining its shape
the idea that is intended
the choicest or most essential or most vital part of some idea or experience
content communicating a message; what something is about
considerable capital (wealth or income)
material of a particular kind or constitution