Continual: The word describes separate actions which are repeated over a period of time. Continuous: The word indicated that an action carries on without stopping or interruption. 2. Principal: The word can be used as both an adjective and a noun. The principal thing or person in a group is the most important one. Principle: The word is only used as a noun. A principle is a basic rule that explains or controls how something works or a guiding rule for behavior. continual continuous I’ve had ____problems with this computer ever since I borrowed it from a friend.