From Apnea Board Wiki
A symptom (from Greek σύμπτωμα, "accident, misfortune, that which befalls", from συμπίπτω, "I befall", from συν- "together, with" + πίπτω, "I fall") is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality. A symptom is subjective, observed by the patient, and not measured.
A symptom may not be a malady, for example symptoms of pregnancy. One could debate, however, that this is an example of common misuse of a word, as the majority of symptoms and the history of the word are related to malady. The proper word for such situations would be "indication" or "suggestion" or simply "sign".