Polylactic acid, or polylactide (PLA) is a thermoplastic polyester with backbone formula (C3H4O2)n or [-C(CH3)HC(=O)O-]n, formally obtained by condensation of lactic acid C(CH3)(OH)HCOOH with loss of water (hence its name).

PLA is a thermoplastic, meaning it will turn into a liquid in its melting point of 150 to 160 Celsius. PLA can be broken down to its original monomers by a thermal de-polymerization process or by hydrolysis.