Why is pea called a dicot plant?

When the seed germinates, the two cotyledons emerge from the soil to form the seed leaves. The seed leaves nourish the plant until it can form its true leaves. (Not all dicots' seed leaves emerge during germination; for example, peas are dicots, but the pea cotyledons remain underground.)

Additional explanation. Above is correct. Within the seed lies the seed embryo monocots have one cotyledon (vein), dicots have two. Dicot roots have one main root called the taproot, where other small roots branch off.