Strong's #5154: tritos (pronounced tree'-tos)
 ordinal from 5140; third; neuter (as noun) a third part, or (as adverb) a (or the) third time, thirdly:--third(-ly).
Thayer's Greek Lexicon:
 ́ 
 
  tritos 
 
 1) the third
 
  Part of Speech: adjective
Relation: ordinal from G5140
  Citing in TDNT: 8:216, 1188
 
Usage:
This word is used 57 times:
Revelation 9:15: "for to slay the  third part of men."
Revelation 9:18: "these three was the  third part of men killed, by the"
Revelation 11:14: "is past; and, behold, the  third woe cometh quickly."
Revelation 12:4: "tail drew the  third part of the stars of heaven, and"
Revelation 14:9: "And  the third angel followed them, saying with a loud"
Revelation 16:4: "And the  third angel poured out his vial upon"
Revelation 21:19: "second, sapphire; the  third, a chalcedony; the fourth, an emerald;"