When two barrel vaults intersect at right angles in architecture, the resulting structure is called a groin vault (also known as a groined vault or cross vault). The intersection creates edges called groins, which are the lines where the two vaults meet. This design efficiently directs the thrust forces to the corners, allowing the vault to be supported mainly at its four corners rather than along long walls, making it structurally more stable and material-efficient compared to a single barrel vault

. In summary:

• Two barrel vaults intersecting at right angles form a groin vault.
• The intersection lines are called groins.
• This design concentrates structural thrust at the corners.
• Groin vaults were first used by the Romans and later became prominent in medieval architecture