By Harold McGee
From the first, the English word nut meant an edible seed surrounded by a hard shell, and this remains the common meaning. Botanists later appropriated the word to refer specifically to one-seeded fruits with a tough, dry fruit layer rather then a fleshy, succulent one. Under this restricted definition, among common nuts only acorns, hazelnuts, beechnuts, and chestnuts qualify as true nuts. The details of anatomy aside, the various seeds that we call nuts differ from grains and legumes in three important ways: they’re generally larger, richer in oil, and require little or no cooking to be edible and nourishing. This combination of qualities made nuts an important source of nourishment in prehistoric times. Today, they’re especially appreciated for their characteristic rich flavor.