So far, the mechanisms leading to the apparently "spontaneous" occurrence of seizures are incompletely understood.

The point is that the monastic system was not just a spontaneous occurrence.

Mosaicism in horses is thought to account for some spontaneous occurrences of white, near-white, spotted, and roan horses.

Although the transitions are nominally "forbidden", there is a small probability of their spontaneous occurrence, should an atom or molecule be raised to an excited state.

A genetic basis, should it exist, might represent either a predisposition for learning the ability or signal the likelihood of its spontaneous occurrence.

Up until the 19th Century, rose hybridization was a spontaneous occurrence, mediated by pollinating insects such as bees, or self-pollination.

Fights that begin after a face-off are usually considered "part of the game," simply spontaneous occurrences that can't be avoided.

This zigzag pattern was not a spontaneous occurrence, nor does it have to continue.

I asked feeling considerably more comfortable with the thought of challenge by appointment than by spontaneous occurrence.

Hockey people often say that fights are spontaneous occurrences that happen in the emotional heat of battle.