Taproot

Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward.

[1] In some plants, such as the carrot, the taproot is a storage organ so well developed that it has been cultivated as a vegetable.

The taproot system contrasts with the adventitious- or fibrous-root system of plants with many branched roots, but many plants that grow a taproot during germination go on to develop branching root structures, although some that rely on the main root for storage may retain the dominant taproot for centuries—for example, Welwitschia.

Dicots, one of the two divisions of flowering plants (angiosperms), start with a taproot,[2] which is one main root forming from the enlarging radicle of the seed.

[4] Many plants with taproots are difficult to transplant, or even to grow in containers, because the root tends to grow deep rapidly and in many species comparatively slight obstacles or damage to the taproot will stunt or kill the plant.

The two types of root systems in plants. The fibrous-root system (A) is characterized by many roots with similar sizes. In contrast, plants that use the taproot system (B) grow a main root, with smaller roots branching off. The letters indicate where the root systems begin.
A dandelion taproot (left) with the rest of the plant (right)
The edible, orange part of the carrot is its taproot