What term describes a restriction on behavior imposed by social custom?

The term that describes a restriction on behavior imposed by social custom is "taboo." A taboo refers specifically to practices or behaviors that are prohibited or restricted by societal norms, and it often carries a strong social stigma. When an action is considered taboo, it typically signifies a deep-rooted belief or cultural norm that discourages individuals from engaging in that behavior due to its perceived immorality or inappropriateness.

While other terms like "norm" can refer to accepted behaviors within a society, they do not necessarily imply prohibition or restriction. Norms describe general expectations and are more about what is typical behavior rather than what is forbidden. Similarly, "rule" usually refers to formal guidelines, often with legal or organizational authority behind them, and "cultural law" is not a standard term widely recognized in sociological contexts. Thus, "taboo" most accurately captures the essence of a behavior restriction rooted in social custom.