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A sideways U with a struck-through bar, excluding the case of equality.
Also known as: Strict subset, Is properly contained in
The proper-subset sign says that one set is contained in another and is not equal to it. Where an author wants to be explicit that the containment is strict, the barred-and-struck form removes the doubt that the plain subset sign carries.
States strict containment: every element of the left set is in the right set and the two sets are not the same.
Contexts: Mathematics
Exists because the plain subset sign is read two different ways; the explicit strict form is used where the distinction carries weight in a proof.
Contexts: Mathematics
A sideways U opening rightwards with a short line beneath it crossed by a small diagonal stroke.