Attribute	Epoxy	Epoxy resin
Refers to	Epoxides / epoxy resins	Epoxides / epoxy resins
CAS Registry Number	Not applicable (class/process term, no single CAS)	Not applicable (class/process term, no single CAS)
Molecular formula	—	—
Molar mass	—	—
Typical name domain	One is the short form, the other the full trade name	One is the short form, the other the full trade name
Chemically different substance?	No	No

Context	Term Used	What Must Be Verified
Chemical nomenclature	Epoxide (oxirane)	A functional group, e.g. glycidyl ethers — CAS assigned per molecule.
Composites/adhesives trade	Epoxy resin	Bisphenol-A diglycidyl ether oligomers (DGEBA) and equivalents.
TDS/SDS documents	State resin type + epoxy equivalent weight (EEW)	EEW defines the curing stoichiometry.

Order by resin type and EEW, not by the word “epoxy”: an epoxide reagent and an epoxy resin are unrelated purchases despite the shared name.

Class and process vocabulary cannot identify an order line. Resolve it to a specific compound (CAS), a concentration or assay basis, and the documentation set the application requires.

Are Epoxy and Epoxy resin chemically identical?

Yes. “Epoxy” is shorthand that names two different things: the epoxide functional group (a three-membered cyclic ether) and epoxy resin, the oligomeric material that cures into a thermoset.

Both refer to the same class/process term.

Which spelling is correct?

Both are accepted, but in different domains: One half is simply shorthand for the other; the expanded form is what should appear in specifications.

Controlled documents should use the qualified form and always add the CAS.

What should a purchase order say?

Name plus CAS plus grade plus quantity. For class terms, the specific compound and its CAS must be named the CAS alone removes every ambiguity created by spelling, shorthand or stereochemistry prefixes.

Is the short form ever a different product?

Yes — and that is precisely why the specification, not the name, decides what ships. One half is simply shorthand for the other; the expanded form is what should appear in specifications.

Editorial note

This article clarifies naming equivalence for procurement and documentation use. It is not legal or regulatory advice; the controlled source for any label is the current monograph, CAS index entry and applicable market regulations.