Common cause failure is defined as the failure resulted due to the common cause fault. The common cause fault is defined as a single source that will cause failure in multiple elements of a system.
In other words, common cause failure are failures of (similar) components due to a shared root cause and not due to the failure of another component in the system.
Some of the common cause failure root cause are environmental dust, humidity, contaminants, radio frequency interference, etc.
The common mode failure often considered synonymous to the common cause failure but as a common cause may have different effects on diverse systems. Therefore common mode failure can be considered as a subset of common cause failure. Common mode failure are common cause failure all of which have the same failure mode and same effects.