What is the term for the amount of air moved in and out of the lungs in one relaxed breath?

The correct term for the amount of air moved in and out of the lungs during one relaxed breath is tidal volume. Tidal volume represents the normal volume of air that is inhaled or exhaled without any added effort, reflecting the efficiency of normal respiratory function.

In contrast, vital capacity refers to the maximum amount of air that can be exhaled after maximum inhalation and involves different respiratory mechanics. Respiratory rate is the frequency of breaths taken in a given time period and does not measure the volume of air exchanged with each breath. Dead space volume accounts for the air that does not participate in gas exchange, thus it reflects a portion of the air that is inhaled but does not reach alveoli where gas exchange occurs. Therefore, tidal volume is specifically concerned with the volume per breath in a relaxed state, which makes it the appropriate term in this context.