Delta(9)-tetrahydrocannabinolic acid is a diterpenoid that is 6a,7,8,10a-tetrahydro-6H-benzo[c]chromene substituted at position 1 by a hydroxy group, positions 6, 6 and 9 by methyl groups and at position 3 by a pentyl group. A biosynthetic precursor to Delta(9)-tetrahydrocannabinol, the principal psychoactive constituent of the cannabis plant. It has a role as an anti-inflammatory agent, a neuroprotective agent, a biomarker and a metabolite. It is a diterpenoid, a benzochromene, a hydroxy monocarboxylic acid, a polyketide and a phytocannabinoid. It is a conjugate acid of a Delta(9)-tetrahydrocannabinolate.