Medical English leans on set collocations, so the exact partner word matters. A clinical diagnosis is a diagnosis a doctor reaches from examining the patient's signs, symptoms, and history rather than from lab or imaging tests. A surgical procedure is an operation, treatment in which a surgeon cuts into the body to repair, remove, or replace something (say this, not "operation procedure"). And adverse effects are the unwanted, harmful reactions a drug can cause, in clinical writing the terms are adverse effects and adverse reactions, while "bad side effects" is understood but too casual for a medical report.
Medical terms travel in fixed pairs
clinical diagnosis /ˈklɪnɪkəl ˌdaɪəɡˈnoʊsɪs/ — From her symptoms and medical history, the doctor reached a clinical diagnosis of early arthritis.
surgical procedure /ˈsɜrdʒɪkəl prəˈsidʒər/ — The surgical procedure took three hours but went without complications.
adverse side effects /ˈædvɜrs ˈsaɪd ɪˌfɛkts/ — Patients were warned about the adverse side effects of the new medication.
Not ""The medication may have bad side effects." ("bad" is too casual for a medical context)" — say ""The medication may have adverse side effects." (the standard clinical term)". In formal medical English the partner is adverse, not "bad." (In clinical writing proper the term is usually adverse effects or adverse reactions.)
Try it: Which phrase fits a formal medical report about a patient's operation? (underwent a surgical procedure / underwent an operation procedure / underwent a surgery procedure) Answer: underwent a surgical procedure — "Surgical procedure" is the standard collocation, with the adjective "surgical" describing the procedure. "Operation procedure" doubles up two nouns and isn't idiomatic, and "surgery procedure" makes the same noun-stacking error; the adjective form is what the fixed phrase needs.
Describing how illnesses behave
When you describe a condition, precise adjectives do the work. An illness that is highly contagious spreads very easily from one person to another ("highly" is the standard written form; "very contagious" is fine in speech). A chronic condition is one that lasts a long time or keeps coming back, while an acute condition comes on suddenly and is severe. Chronic and acute are opposites, not synonyms: chronic is about how long it lasts, acute about how sharply and quickly it strikes.
highly contagious /ˈhaɪli kənˈteɪdʒəs/ — Measles is highly contagious, so the ward was closed to visitors.
chronic /ˈkrɑnɪk/ — She manages her chronic back pain with physiotherapy and gentle exercise.
acute /əˈkjut/ — He was rushed in with acute chest pain late on Sunday night.
Not ""The virus is very contagious." ("very" is fine casually but weak in a medical report)" — say ""The virus is highly contagious." (the standard medical intensifier)". In clinical English, contagious pairs with highly, "very" is not wrong, just weaker on the page. And don't confuse chronic (long-lasting) with acute (sudden and severe); they are opposites, not synonyms.
Try it: A patient has had mild joint pain for over ten years. How would a doctor describe it? (a chronic condition / an acute condition / a contagious condition) Answer: a chronic condition — "Chronic" means long-lasting, which fits pain lasting over ten years. "Acute" would mean sudden and severe, the opposite of a decade-long mild ache, and "contagious" describes something that spreads between people, which joint pain does not.