Grain is a fruit not seed.

Explanation

**Step-by-Step Solution:**

1. **Definition of Grain**: A grain is defined as a type of fruit that is specifically known as a caryopsis. This is a unique type of fruit that is characteristic of flowering plants, particularly in the family Poaceae (grasses).

2. **Structure of Grain**: In grains, the outer layer, known as the pericarp, is fused with the seed coat. This fusion means that the grain does not have a separate seed coat; instead, the seed and fruit are combined into a single structure.

3. **Monocotyledon Classification**: Grains are classified as monocotyledons (monocots), which means they have one cotyledon in their seeds. This classification is important in understanding their structure and development.

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