It's often used in medical terms to describe different aspects of breathing, such as:
* Apnea: Absence of breathing.
* Dyspnea: Difficulty breathing.
* Eupnea: Normal breathing.
* Hyperpnea: Increased rate and depth of breathing.
* Orthopnea: Difficulty breathing when lying down.
* Tachypnea: Rapid breathing.
So, whenever you see "-pnea" in a medical term, it's related to the act of breathing!