installment

Concise Oxford English Dictionary © 2008 Oxford University Press:
instalment /ɪnˈstɔːlmənt/ (US also installment)

▶noun

• 1 a sum of money due as one of several equal payments for something, spread over an agreed period of time.

• 2 one of several parts of something which are published or broadcast in sequence at intervals.

– origin C18: alt. of obs. estalment (prob. by assoc. with installation), from Anglo-Norman Fr. estalement, from OFr. estaler ‘to fix’.