Why are grass grains considered both seeds and fruits?

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Cluster of bright red seeds emerging from the cone-shaped fruit of a magnolia grandiflora, surrounded by large, glossy green leaves. — Seed Fruit and seeds of the southern magnolia (*Magnolia grandiflora*). The fruit is an aggregate of follicles, and each follicle bears a single red seed.

Grass grains are considered both seeds and fruits because of their unique botanical structure, known as a caryopsis.

In most flowering plants, the seed is a discrete unit contained within a fruit, which develops from the plant's ovary. However, in grasses, the outer seed coat (integument) and the ovary wall are completely fused together. Because this fusion makes the two structures inseparable without specialized milling, the entire unit functions as a single entity.123

Botanically, this structure is a dry, one-seeded fruit, but because it contains the embryo and nutrient tissue necessary for reproduction, it is also functionally a seed. Consequently, these grains are often described as diaspores—or dispersal units—that combine the characteristics of both seeds and fruits.241