Are to perish with the using (estin ei pqoran th apocrhsei). Literally, "are for perishing in the using." Pqora (from pqeirw) is old word for decay, decomposition. Apocrhsi (from apocraomai, to use to the full, to use up), late and rare word (in Plutarch), here only in N.T. Either locative case here or instrumental. These material things all perish in the use of them.