What is "isonicotinic acid"

n. (context organic compound English) An isomer of nicotinic acid, ''pyridine-4-carboxylic acid''

Isonicotinic acid or 4-pyridinecarboxylic acid is an organic compound with the formula CHN(COH). It is a derivative of pyridine with a carboxylic acid substituent at the 4-position. It is an isomer of picolinic acid and nicotinic acid which has the carboxyl group at the 2nd and 3rd position respectively compared to the 4-position for nicotinic acid.