in·stall·ment 1 also in·stal·ment 
(ĭn-stôlmənt)
(ĭn-stôlmənt)n.
1. One of a number of successive payments in settlement of a debt.
2.
a. A portion of something, such as a publication, issued at intervals.
b. A chapter or part of a literary work presented serially.
[Alteration of obsolete estallment, from Anglo-Norman, from Old French estaler, to place, fix, from estal, place, of Germanic origin; see stel- in the Appendix of Indo-European roots.]