instalment, n. (US installment)
1 a sum of money due as one of several usu. equal payments for something, spread over an agreed period of time.
2 any of several parts, esp. of a television or radio serial or a magazine story, published or shown in sequence at intervals.
instalment plan payment by instalments, esp. hire purchase.
alt. f. obs. estallment f. AF estalement f. estaler fix: prob. assoc. with INSTALLATION