23 years old , missed period , not sexually active , spends time in the gym and eating healthy. do i have amenorrhea ?

Amenorrhea: You don't have primary amenorrhea, because you did have a menstrual period before. Skipping one cycle does not qualify for secondary amenorrhea. If you are worried, see a gynecologist and have them do blood tests to check your thyroid gland and your pituitary gland.

Yes: all amenorrhea means is missed period. so yes. can be from pregnancy, normal missed period, thyroid, underweight, lots of reasons. stress is a biggie, can miss period 6 months after even good life changes.