1 : coming from another source and not inherent or innate
2 : arising or occurring sporadically or in other than the usual location
"As sand accumulates, the stems elongate, and adventitious roots develop, allowing the plants to seek out water and nutrients in successive layers of accumulating sand." -- From Julie Laity's 2008 book Deserts and Desert Environments
"Lately, however, a new kind of biography has been slouching into view. There is, in fact, a mini-boom in multiple lives, books that explore the adventitious connections between assorted near-contemporaries." -- From an article by Robert McCrum in The Observer (England), July 10, 2011
Did You Know?
"Adventitious" is an adventitious word: it comes to English from the Latin "adventicius," meaning "coming from outside." This, in turn, comes from "adventus," the past participle of the verb "advenire," meaning "to arrive" or "to happen." That verb is also a source of several other English words, including "advent" (which, in its uncapitalized form, can refer to any coming or arrival), "adventure" (a word whose earliest sense was "chance happening"), and "avenue" (a means of arrival).
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