Hydrates and anhydrous substances

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Modeling

Parent concept	Most distal appropriate descendant of 105590001 |Substance (substance)|
Semantic tag	(substance)
Definition status	Primitive
Attribute	738774007 |Is modification of (attribute)| relationship to the substance with unspecified hydration 726542003 |Has disposition (attribute)|, as appropriate

Hydrates

Hydates are modeled with an 738774007 | Is modification of (attribute)| relationship to the substance with unspecified hydration.

For example,

• Ferrous oxalate dihydrate (substance) is modification of → Ferrous oxalate

• Caffeine hydrate (substance) is modification of → Caffeine

• Zinc sulfate heptahydrate (substance) is modification of → Zinc sulfate

Naming

FSN

Pattern:

• X hydrate (substance)

• X dihydrate (substance)

• X monohydrate (substance)

For example,

• Copper sulfate pentahydrate (substance)

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Preferred Term

Pattern:

• X hydrate

• X dihydrate

• X monohydrate

For example,

• Copper sulfate pentahydrate

Exemplar

The following illustrates the inferred view.

Caffeine hydrate (substance) IS MODIFICATION OF Caffeine (substance)

Anhydrous compounds

Anhydrous compounds have an 738774007 | Is modification of (attribute)| relationship to the unspecified substance, i.e., where the level hydration is not specified.

For example,

• Sodium carbonate anhydrous (substance) is modification of → Sodium carbonate

• Theophylline anhydrous (substance) is modification of → Theophylline

Naming Guidelines

FSN

Pattern:

• X anhydrous (substance)

For example,

• Theophylline anhydrous (substance)

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Preferred Term

Pattern:

• X anhydrous

For example,

• Theophylline anhydrous

---

Synonyms

Anhydrous X

Exemplar

The following illustrates the inferred view.

|Theophylline anhydrous (substance)| IS MODIFICATION OF |Theophylline (substance)|

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