A limit state is a state of impending failure beyond which the structure ceases to perform its intended function satisfactorily, in terms of either safety or serviceability; i.e. it either collapses or becomes unserviceable. There are 2 kinds of limit states: 1. Ultimate limit states / Limit state of collapse, which deals with strength, overturning, sliding, buckling, fatigue, fracture, etc 2. Serviceability limit states, which deals with discomfort to occupancy and/or malfunction due to excessive deflection, crack-width, vibration, leakage, etc.