The temperature at which air becomes saturated and moisture condenses. Chesapeake summer dew points in the 70s are why AC coils here work overtime and why basements sweat — it's a better mugginess gauge than relative humidity alone.
Air-quality terms map to humidity control in muggy Chesapeake summers, filtration (MERV), ventilation for tighter renovated homes, and duct condition in houses that have seen decades of retrofits.