These are olives that have been allowed to ripen on the tree. American recipes that call for black olives are probably referring to the Mission olive. Other varieties of black olives are the Aleppo, Alphonso, Amphissa, black Cerignola, Gaeta, black Greek, Kalamata, Ligurian, Lugano, Moroccan dry-cured, Niçoise, Nyons, Ponentine, and Royal.
Plural: Black olives
Season: available year-round