From airo; a number (as reckoned up) -- number.
see GREEK airo
a. a fixed and definite number: τόν ἀριθμόν πεντακισχίλιοι, in number, John 6:10 (2 Macc. 8:16; 3Macc. 5:2, and often in Greek writings; Winers Grammar, 230 (216); (Buttmann, 153 (134))); ἐκ τοῦ ἀριθμοῦ τῶν δώδεκα, Luke 22:3; ἀριθμός ... ἀνθρώπου, a number whose letters indicate a certain man, Revelation 13:18.
b. an indefinite number, equivalent to a multitude: Acts 6:7; Acts 11:21; Revelation 20:8.