Lucas 24:33

They rose up the same hour,— As soon as Jesus departed, the two disciples made all the haste they could to Jerusalem, that they might have the pleasure of acquainting their brethrenwith the agreeable news; but they were in some measure prevented: for immediately on their arrival, the eleven, with the women, accosted them, giving them the news of their Master's resurrection. The eleven was the current stile for the whole college of apostles; and afterthe call of Matthias to the apostleship, they were again called the twelve. In virtue of this stile, a general meeting of the apostles is called a meeting of the eleven, or the twelve, though one or more may happen to be absent.

This is agreeable to both antient and modern usage, in the case of senates, councils, and the like. Hence it is that St. Luke says the eleven were gathered together, though it appears that Judas was dead, and that Thomas was absent, Juan 20:24. St. Paul, 1 Corintios 15:5 calls it a meeting of the twelve, because he was not converted till after the election of Matthias, when that again came to be the usual stile.