When two or more events occur in a way that one event is the result of another, they have a cause-and-effect relationship. For example, when a baby cries upon hearing a loud noise, the loud noise is the cause and the baby's crying is the effect.
Such cause-and-effect relationships are also observed in nature. Lightning is always followed by thunder. The cause-and-effect relationship can be seen clearly between heavy rain and consequent flooding. Lack of rainfall leads to drought; excessive exposure to direct sunlight causes sunburn. The cause-and-effect relationship is present whenever one event could not have occurred without a preceding event.