adventitious

Adventitious is an adjective describing something that arises, occurs, or is introduced from outside rather than from the place or tissue in question. It often implies a secondary, incidental, or external origin. The term is widely used across disciplines to flag extrinsic origin or development.

In botany, adventitious refers to organs that form from non-meristematic tissue. Adventitious roots grow from stems, leaves, or other tissues rather than from the plant’s vascular cambium, frequently in response to injury, stress, or for vegetative propagation. Adventitious shoots or buds can develop on parts of a plant that do not normally produce them, enabling regeneration or cloning. In plant tissue culture, adventitious rooting or embryogenesis may be induced from callus or somatic tissue, supporting clonal propagation and plant regeneration.

In medicine and clinical contexts, adventitious describes findings or phenomena not normally present in a healthy organism. Adventitious breath sounds, such as crackles, wheezes, or rhonchi, can indicate underlying pulmonary conditions, including infection, fluid accumulation, or airway obstruction. The term also appears in other medical settings to denote extraneous materials or responses arising outside the usual anatomy or physiology.

Etymology traces adventitious to Latin adventicius, from adventus meaning “arrival,” reflecting the sense of coming from the outside. The word is used to distinguish spontaneous, native development from externally derived or encountered phenomena.