They have as king: according to Pro 30.27 locusts have no king, but these demonic beings have one. Their king is the angel of the bottomless pit, that is, the angel in charge of, looking after or taking care of, the abyss. For the translation of bottomless pit or “abyss,” see 9.1.

In Hebrew: in many languages this will be rendered as “in the Hebrew language.”

Abaddon: this is the Hebrew word for “destruction” (or, “place of destruction”) as a name for Sheol, as in Job 26.6 (parallel with Sheol); 28.22 (Abaddon and Death); Psa 88.11b (parallel with grave); Pro 15.11 (Sheol and Abaddon).

The Greek word Apollyon means “Destroyer.” It appears only here in the New Testament. In Greek: see the comment on Hebrew above. Translators are urged to imitate Good News Translation, which gives in the text itself the meaning of the Greek word.

Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .