1 [noncount] : the act of identifying a disease, illness, or problem by examining someone or something
- The unusual combination of symptoms made accurate diagnosis difficult.
- She is an expert in the diagnosis and treatment of eye diseases.
2 [count] : a statement or conclusion that describes the reason for a disease, illness, or problem
- The diagnosis was a mild concussion.
- His doctor made an initial diagnosis of pneumonia.
- The committee published its diagnosis of the problems affecting urban schools.