A.T. Robertson Commentary Revelation 9:16

"And the number of the armies of the horsemen was twice ten thousand times ten thousand: I heard the number of them." — Revelation 9:16 (ASV)

Of the horsemen (του ιππικου). Old adjective ιππικος from ιππος (horse), equestrian. The neuter articular singular το ιππικον, the horse or the cavalry in contrast with το πεζικον (the infantry), here only in N.T. For the numbers here see on 5:11; 7:4.