What is "adventitiousness"

Adventitious \Ad`ven*ti"tious\, a. [L. adventitius.]

1. Added extrinsically; not essentially inherent; accidental or causal; additional; supervenient; foreign.

   To things of great dimensions, if we annex an adventitious idea of terror, they become without comparison greater.
   --Burke.

2. (Nat. Hist.) Out of the proper or usual place; as, adventitious buds or roots.

3. (Bot.) Accidentally or sparingly spontaneous in a country or district; not fully naturalized; adventive; -- applied to foreign plants.

4. (Med.) Acquired, as diseases; accidental. [1913 Webster] -- Ad`ven*ti"tious*ly, adv. -- Ad`ven*ti"tious*ness, n.

n. the degree to which a thing is adventitious

Adventitious has various meanings in various disciplines and in general usage.

Adventitious is from the Latin root advenire, meaning "to come to" and in English the meanings tend to have connections to "accidental/ casual occurrence", "arising from without; supervenient, 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.