Heterocyclic Compounds, 3-Ring

**Definition:** A class of heterocyclic compounds that include a three-ring fused structure. Both aromatic or non-aromatic ring structures are included in this category.

**Tree numbers:** - D03.633.300

**Synonyms:** - Fused Heterocyclic Compounds, Three-Ring - Three Ring Heterocyclic Compounds - Heterocyclic Cpds, 3 Ring