Feminine noun · Feminine of the ord. of πεντήκοντα (G4004)
Feminine of the ordinal of G4004; fiftieth (G2250 being implied) from Passover, i.e. the festival of "Pentecost":—Pentecost.
Outline
Pentecost = "the fiftieth day"
the second of the three great Jewish feasts, celebrated at Jerusalem yearly, the seventh week after the Passover, in grateful recognition of the completed harvest