accidental

accidental is an Adverb

Definition:

[1] Happening by chance, or unexpectedly; taking place not according to the usual course of things; casual; fortuitous; as, an accidental visit.

[2] Nonessential; not necessary belonging; incidental; as, are accidental to a play. Accidental chords (Mus.), those which contain one or more tones foreign to their proper harmony. -- Accidental colors (Opt.), colors depending on the hypersensibility of the retina of the eye for complementary colors. They are purely subjective sensations of color which often result from the contemplation of actually colored bodies. -- Accidental point (Persp.), the point in which a right line, drawn from the eye, parallel to a given right line, cuts the perspective plane; so called to distinguish it from the principal point, or point of view, where a line drawn from the eye perpendicular to the perspective plane meets this plane. -- Accidental lights (Paint.), secondary lights; effects of light other than ordinary daylight, such as the rays of the sun darting through a cloud, or between the leaves of trees; the effect of moonlight, candlelight, or burning bodies. Fairholt.