(biology) Any organism found in surroundings, or in association with another organism, in which it is normally absent

A sharp, pointy object, such as a sliver or splinter. / A bur; a seed pod with sharp features that stick in fur or clothing. / A small piece of material left on an edge after a cutting operation.

(organic chemistry) An alkaloid found in ragwort (Jacobaea vulgaris).

plural of certification