|Easton's Bible Dictionary|
The tiara of a king (Ezek. 21:26; Isaiah 28:5; 62:3); the turban (Job 29:14). In the New Testament a careful distinction is drawn between the diadem as a badge of royalty (Revelation 12:3; 13:1; 19:12) and the crown as a Mark of distinction in private life. It is not known what the ancient Jewish "diadem" was. It was the Mark of Oriental sovereigns. (see CROWN.)
Noah Webster's Dictionary
1. (n.) Originally, an ornamental head band or fillet, worn by Eastern monarchs as a badge of royalty; hence (later), also, a crown, in general.
2. (n.) Regal power; sovereignty; empire; -- considered as symbolized by the crown.
3. (n.) An arch rising from the rim of a crown (rarely also of a coronet), and uniting with others over its center.
4. (v. t.) To adorn with a diadem; to crown.
Int. Standard Bible Encyclopedia
di'-a-dem: There are seven Bible references to the diadem, four in the Old Testament and three in the New Testament. The Hebrew words do not mark any clear distinctions.
(1) tsaniph, tsanoph, tsaniphah (all from tsanaph, primarily "to wrap," "dress," "roll") mean a headdress in the nature of a turban or piece of cloth wrapped or twisted about the head. The word is also rendered "hood," "mitre." Job 29:14: "My justice was as a robe and a diadem" (RVm, "turban"); Isaiah 62:3: "a royal diadem in the hand of thy God."
(2) tsephirah, means "a crown," "diadem," i.e. something round about the head; Isaiah 28:5 "a diadem of beauty, unto the residue of his people."
(3) mitsnepheth, means an official turban or tiara of priest or king, translated also "mitre." Ezekiel 21:26: "Remove the mitre, and take off the crown."
(4) diadema, the Greek word in the New Testament for "diadem," means "something bound about the head." Found 3 t, all in Revelation 12:3: "a great red dragon. and upon his heads seven diadems" (the King James Version "crowns"); Revelation 13:1: "a beast. and on his horns ten diadems"; 19:11, 12: "a white horse. and upon his head are many diadems." See CROWN.
William Edward Raffety
Diadem (9 Occurrences)
Exodus 29:6 And thou shalt put the turban upon his head, and fasten the holy diadem to the turban, (DBY NIV)
Exodus 39:30 And they made the thin plate, the holy diadem, of pure gold, and wrote on it with the writing of the engravings of a seal, Holiness to Jehovah! (DBY NIV)
Leviticus 8:9 and he put the turban upon his head; and upon the turban, on the front of it, he put the golden plate, the holy diadem; as Jehovah had commanded Moses. (DBY NIV)
Job 29:14 I put on righteousness, and it clothed me. My justice was as a robe and a diadem. (WEB KJV JPS ASV WBS YLT)
Isaiah 28:5 In that day, Yahweh of Armies will become a crown of glory, and a diadem of beauty, to the residue of his people; (WEB KJV JPS ASV DBY WBS YLT NAS RSV)
Isaiah 61:10 I will greatly rejoice in Jehovah, my soul shall be joyful in my God; for he hath clothed me with the garments of salvation, he hath covered me with the robe of righteousness, as a bridegroom decketh himself with a garland, and as a bride adorneth herself with her jewels. (See JPS)
Isaiah 62:3 You shall also be a crown of beauty in the hand of Yahweh, and a royal diadem in the hand of your God. (WEB KJV JPS ASV DBY WBS YLT NAS RSV NIV)
Ezekiel 21:26 Thus saith the Lord GOD; Remove the diadem, and take off the crown: this shall not be the same: exalt him that is low, and abase him that is high. (KJV WBS)
Zechariah 3:5 He also said, 'Let them set a pure diadem on his head. And they set the pure diadem on his head, and clothe him with garments. And the messenger of Jehovah is standing, (YLT)