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The volume of air remaining in the lungs after a normal tidal volume expiration is referred to as Functional Residual Capacity (FRC). FRC is the sum of the residual volume and the expiratory reserve volume, essentially representing the amount of air that remains in the lungs at the end of a passive expiration. This measurement is crucial as it reflects the equilibrium point of the lung's elastic recoil and the thoracic cavity, ensuring that gas exchange can continue between breaths.

Vital capacity, on the other hand, is a measure of the maximum amount of air a person can expel from the lungs after a maximum inhalation and does not pertain to air remaining after normal breathing. Residual volume refers specifically to the air that remains in the lungs after a maximal exhalation, but does not encompass the additional volume contributed by the expiratory reserve volume. Total lung capacity is the total volume of air that the lungs can hold, which includes all lung volumes but does not specifically address the volume remaining after a normal tidal expiration. FRC specifically captures the air left to facilitate continuous gas exchange, which is essential for respiration.