The word respiratory is an adjective describing anything related to respiration: how we breathe.
In addition to the nervous, muscular, and skeletal systems, the body has a respiratory system: this is how we get and use oxygen, which we need to survive. The respiratory system also expels carbon dioxide, which we don’t use. The main respiratory organs are the lungs. Asthma and bronchitis are respiratory diseases, because they make breathing difficult. When you see the word respiratory, just take a deep breath and you’ll remember the meaning.