breathlessness

noun2

1. •
   The state of being breathless or out of breath, especially merely temporarily from exertion.

   • Climbing eight flights of stairs while the elevator is out of service can easily produce some breathlessness in people whose physical fitness is otherwise not noticeably impaired.
2. •
   Difficult or labored breathing, as a symptom or sign of a medical condition.

   • Since he'd entered the urgent care center, his breathlessness had only gotten worse, even though he'd been sitting quietly.