Green olives by John Spottiswood.

Green olives are picked from the tree before they're completely ripened. The most common variety is the Manzanilla olive, which is often pitted and stuffed. Other green olives varieties include the Agrinion, Arauco, Arbequina, Atalanta, green Cerignola, cracked Provençal, Kura, Lucque, Nafplion, Picholine, Sevillano, and Sicilian. Substitutes: black olives (usually softer in texture) OR caper berries (as a garnish for martinis) OR cocktail onions (This turns a martini into a Gibson.)