Is it ensure, insure, or assure?
late 15c., from Middle French convalescence (15c.), from Late Latin convalescentia "regaining of health," from convalescentem (nominative convalescens), present participle of convalescere (see convalesce).
convalescence con·va·les·cence (kŏn'və-lěs'əns)
Gradual return to health and strength after an illness, an injury, or a surgical operation.
The period needed for returning to health after an illness, an injury, or a surgical operation.