The Collaborative International Dictionary
Decury \Dec"u*ry\, n.; pl. Decuries. [L. decuria, fr. decem
ten.]
A set or squad of ten men under a decurion.
--Sir W. Raleigh.
Wiktionary
n. (context historical English) A set or squad of ten men under a decurion.
Wikipedia
In Ancient Rome, a decury ( Latin decuria) was a group of ten people, ranged under one chief, or commander, called a decurio. The Roman cavalry was divided into decuries.
Romulus divided the whole Roman people into three tribes; over each of which he appointed a tribune. Each tribe he subdivided into ten centuries, with centurions at their heads. And, each century he subdivided further into ten decuries, over each of which a decurio commanded.
In the interregnum after the death of Romulus the Roman senate, comprised at that time of 100 men, arranged itself into ten decuries, and each decurio governed Rome for five days as interrex. The decurios continued to rotate the government amongst themselves for a year until the election and accession of Numa Pompilius.
Usage examples of "decury".
Before the age of Justinian, or perhaps of Diocletian, the decuries of Roman judges had sunk to an empty title: the humble advice of the assessors might be accepted or despised.