Complex sentence: What is usually meant by assumption of risk is more precisely termed "primary" assumption of risk occurs when the plaintiff has either expressly or impliedly relieved the defendant of the duty to mitigate or relieve the risk causing the injury from which the cause of action arises.
Split into simpler sentences: What is usually meant by assumption of risk is more precisely termed "primary" assumption of risk. It occurs when the plaintiff has either expressly or impliedly relieved the defendant of the duty to mitigate or relieve the risk causing the injury from which the cause of action arises.