intransitive verb
Definition: To go back to a previous condition, especially after having improved or recovered from something, like an illness or bad habit.
Example: After several months of feeling better, he experienced a relapse and had to return to the hospital.
noun
Definition: A return to a previous condition, especially after a period of improvement, often related to health or behavior.
Example: After several months of recovery, he experienced a relapse and had to start treatment again.