Air vents are common fixtures in buildings and vehicles that provide a passage for air to flow in and out. However, there are several synonyms for the word "air vent" that may be used interchangeably. Some of these synonyms include "air duct," "air grille," "air diffuser," "air register," and "ventilation grille." They all serve the same purpose of allowing air circulation and improving air quality in a closed environment. The choice of which word to use may depend on the specific context or design of the structure where it is placed. But whatever name it is called, air vents remain essential for maintaining comfort and safety in any enclosed space.