con·va·lesce 
(kŏn′və-lĕs)
(kŏn′və-lĕs)intr.v. con·va·lesced, con·va·lesc·ing, con·va·lesc·es
To return to health and strength after illness; recuperate.
[Late Middle English convalesshe, from Latin convalēscere : com-, intensive pref.; see COM- + valēscere, to grow strong, inchoative of valēre, to be strong; see wal- in the Appendix of Indo-European roots.]