- A yellow crystalline organic compound, C<sub>13</sub>H<sub>10</sub>O, that is soluble in ether and is used as a fungicide and in organic synthesis. The structural unit of xanthene is a feature in several fluorescent dyes.
- Orthomethylenediphenylene oxid; a colorless compound, , prepared by the action of aluminium chlorid on phenol. It crystallizes in plates, melts at 100.5° C., and boils at 315° C.
- any of a group of <xref>tricyclic</xref> <xref>heterocycles</xref> (<xref>dibenzopyrans</xref>) that are the basis for a range of <xref>dyes</xref> such as <xref>fluorescein</xref> and <xref>eosin</xref>