Select the most appropriate one-word substitution for the given group of words. Recovering from an illness or medical treatment.

Convalescent

The most appropriate one-word substitution for "recovering from an illness or medical treatment" is convalescent.

• Bohemian refers to a person who lives an unconventional or artistic lifestyle.
• Connoisseur refers to a person who is an expert in a particular field, especially the fine arts.
• Convalescent refers to a person who is recovering from an illness or medical treatment.
• Cosmopolitan refers to a person who is familiar with or at home in many different countries or cultures.

Convalescent is the most appropriate word because it specifically refers to the process of recovering from an illness or medical treatment. It is derived from the Latin word convalescens, meaning "to become strong again."