What is the correct term for something that is fitting or suitable?

The term "appropriate" directly refers to something that is fitting, suitable, or right for a particular situation or context. In various professional and everyday contexts, using the term "appropriate" indicates that an action, response, or object aligns well with the requirements or standards expected. This word is commonly used in healthcare, education, and social interactions to denote that something meets the necessary criteria or standards.

The other terms do not have this meaning. "Exacerbation" refers to the worsening of a condition, particularly in medical contexts, and does not convey the idea of suitability. "Motionless" describes a lack of movement, which is unrelated to the concept of fitting or appropriate. "Hypercapnia" is a medical term that refers to an excess of carbon dioxide in the bloodstream, again not connecting to the notion of something being suitable or fitting. Thus, "appropriate" stands out as the correct term in this context.