Another kind of mixed structure, called faulty predication, occurs when a subject and predicate do not fit together grammatically or simply do not make sense together. Many cases of faulty predication result from using forms of be when another verb would be stronger.

A person is not a characteristic.

Rules cannot expect anything.

Is when, is where, and the reason…is because

Constructions using is when, is where, and the reason…is because are used frequently in informal contexts, but they may be inappropriate in academic writing because they describe a noun using an adverb clause (31m).