What medical terms mean return symptoms of a disease?

Relapse: the reappearance of the symptoms of a disease after a period of improvement or remission.

Recurrence: the return of a disease after it has been treated and apparently cured.

Recrudescence: the intensification or exacerbation of the symptoms of a disease after a period of quiescence.

Exacerbation: a worsening of the symptoms of a disease.

Flare-up: a sudden increase in the intensity of the symptoms of a disease.