Final answer:
A groin vault is a type of vault that springs from an abutment higher at one side than at the other. It is easily identified by the x-shape it creates in the ceiling.
Step-by-step explanation:
A vault that springs from an abutment higher at one side than at the other is called a groin vault. This type of vault is easily identified by the x-shape it creates in the ceiling. The thrust of the groin vault is concentrated along this x-shape, allowing for manipulation of the space below.