GO:0031427

Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a methotrexate stimulus. Methotrexate is 4-amino-10-methylformic acid, a folic acid analogue that is a potent competitive inhibitor of dihydrofolate reductase. [CHEBI:44185, GOC:ef, GOC:mah, ISBN:0198506732]