A fibrous root system (sometimes also called adventitious root system) is the opposite of a taproot system. It is usually formed by thin, moderately branching roots growing from the stem. A fibrous root system is universal in monocotyledonous plants and ferns.In a plant with a taproot system, the taproot is the largest, most central, and most dominant root. Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward. In plants with taproot systems, the taproot is the central root from which other roots sprout laterally.
Adventitious has various meanings in various disciplines and in general usage.Adventitious is from the Latin root adventure, meaning "to come or be super added" and in correct English the meanings tend to have connections to accidental or casual occurrence. "...of the nature of an addition from without; supervention, accidental, casual.People sometimes speak of an event or occurrence as being "random", when the word "adventitious", or perhaps "accidental", might be more strictly correct.