The words care, therapy, treatment, and intervention overlap in a semantic field, and thus they can be synonymous depending on context. Moving rightward through that order, the  connotative level of holism decreases and the level of specificity (to concrete instances) increases. Thus, in health-care contexts (where its  senses are always noncount), the word care tends to imply a broad idea of everything done to protect or improve someones health (for example, as in the terms  preventive care and primary care, which connote ongoing action), although it sometimes implies a narrower idea (for example, in the simplest cases of wound care or  postanesthesia care, a few particular steps are sufficient, and the patients interaction with the provider of such care is soon finished). In contrast, the word intervention tends to be specific and concrete, and thus the word is often  countable; for example, one instance of cardiac catheterization is one  intervention performed, and  coronary care (noncount) can require a series of interventions (count). At the extreme, the piling on of such countable interventions amounts to  interventionism, a flawed model of care lacking holistic  circumspection—merely treating discrete problems (in billable increments) rather than maintaining health. Therapy and treatment, in the middle of the semantic field, can connote either the holism of care or the discreteness of intervention, with context conveying the intent in each use. Accordingly, they can be used in both noncount and count senses (for example, therapy for chronic kidney disease can involve several  dialysis treatments per week).
The words aceology and iamatology are obscure and obsolete synonyms referring to the study of therapies.
The English word therapy comes via Latin therapīa from  and literally means "curing" or "healing". The term  is a somewhat archaic doublet of the word therapy.