adventitious

UK: /ˌædvɛnˈtɪʃəs/ US: (ad′vən tish′əs)

WordReference Random House Unabridged Dictionary of American English © 2025

ad•ven•ti•tious  (ad′vən tish′əs), adj. 

1. associated with something by chance rather than as an integral part;
   extrinsic.
2. Botany, Zoology appearing in an abnormal or unusual position or place, as a root.

• Latin adventīcius literally, coming from without, external, equivalent. to ad- ad- + ven- (stem of venīre to come) + -t(us) past participle suffix + -īcius -itious
• 1595–1605

ad′ven•ti′tious•ly, adv. 
ad′ven•ti′tious•ness, n. 

Collins Concise English Dictionary © HarperCollins Publishers::

adventitious / ˌædvɛnˈtɪʃəs/ adjective

1. added or appearing accidentally or unexpectedly
2. (of a plant or animal part) developing in an abnormal position, as a root that grows from a stem

Etymology: 17th Century: from Latin adventīcius coming from outside, from adventus a coming

ˌadvenˈtitiously adverb