The phrase "primary symptom" refers to the main or most important sign of a problem or illness. It is the key thing that indicates something might be wrong. Full definition
Primary symptoms of menopause often have to do with the decrease in ovarian hormone production. (hghinjections.us)
It consists of 90 items and yields nine scores along primary symptom dimensions and three scores that refer to global distress indexes. (frontiersin.org)
For example, canine circovirus — a disease whose primary symptoms are intestinal disturbances — can be fatal to dogs, as it causes internal bleeding. (cuteness.com)