This verb means to assign someone to a group by counting them in. Acts 1:17 uses the perfect passive participle to describe Judas: he 'was numbered among us,' having been officially counted as one of the Twelve. The perfect tense emphasizes the completed state—he had been and remained (until his betrayal) part of the apostolic band. Classical usage shows counting in a census or reckoning someone among a group. The cross-linguistic evidence emphasizes the formal, official nature of the counting. Peter's speech acknowledges Judas's legitimate apostolic position before his fall.