1: ἱππεύς
(Strong's #2460 — Noun Masculine — hippeus — hip-yooce' )

"a horseman," is used in the plural in Acts 23:23,32 .

2: ἱππικός
(Strong's #2461 — Adjective — hippikos — hip-pee-kon' )

an adjective signifying "of a horse" or "of horsemen, equestrian," is used as a noun denoting "cavalry," in Revelation 9:16 , "horsemen," numbering "twice ten thousand times ten thousand," RV.