Triazine

Not to be confused with triazene; triazane; or hexahydro-1,3,5-triazine.
The three isomers of triazine, with ring numbering

Triazines are a class of nitrogen-containing heterocycles. The parent molecules' molecular formula is C3H3N3. They exist in three isomeric forms, 1,3,5-triazines being common.