Answer
A nuisance per se is an act, occupation, or structure that is a nuisance at all times and under all circumstances, regardless of its location or surroundings — it is a nuisance in and of itself, such as a thing that is a direct menace to public health or safety. A nuisance per accidens is a nuisance only because of the particular location, surroundings, or manner in which it is conducted or maintained; a lawful and useful business may become a nuisance per accidens by reason of the circumstances.
The distinction is decisive for how a nuisance may be abated. A nuisance per se may be summarily abated without judicial proceedings. A nuisance per accidens may not — it requires a prior judicial determination that the thing is in fact a nuisance before it may be abated, because whether it is a nuisance depends on evidence of the surrounding facts.
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