Factor of safety and Safety margin

Factor of safety noun - The ratio of the breaking stress of a structure to the estimated maximum stress in ordinary use.

Safety margin and factor of safety are semantically related. In some cases you can use "Safety margin" instead a noun phrase "Factor of safety".

Safety margin noun - The margin required in order to insure safety.

Factor of safety and safety margin are semantically related. You can use "Factor of safety" instead a noun phrase "Safety margin".