From Seed to Seed:
Plant Science for K-8 Educators

Nuts. Many of the foods to which we commonly refer as nuts are not true nuts. However, we'll group them together here for convenience. A true nut, botanically speaking, is a dry, one-seeded fruit. Nuts are indehiscent, meaning the seeds remain in the fruit after the fruit is shed from the parent plant. Examples of true nuts include acorns and hazelnuts (filberts).

Almonds and walnuts are technically the seeds of fleshy, one-seeded fruits (drupes), and are thus not true nuts. Almonds come from a peach-like fruit. In peaches, we eat the sweet flesh and discard the "pit"; in almonds, we discard the fibrous flesh and keep the pit. The edible portion of the almond is contained within a hard hull. Walnuts are also contained within a very sturdy hull.

Although they dry and store fairly well, nuts are not a significant source of food for most of the human population, in part because they are difficult to harvest mechanically. Nuts are concentrated sources of oil, and have proportionally fewer carbohydrates than cereals or legumes.