What instrument is used to measure airflow velocity?

An anemometer is specifically designed to measure airflow velocity, making it the correct choice for this question. It typically functions by utilizing rotating cups or blades that respond to the wind or air passing over them, allowing it to provide a direct measurement of how fast the air is moving.

In contrast, a hygrometer measures the humidity in the air, providing data about moisture levels rather than airflow. A thermometer measures temperature, which is unrelated to air velocity. Lastly, a manometer is used to measure pressure differences, which could be related to airflow but does not directly measure velocity. Thus, the anemometer is clearly the appropriate instrument for assessing airflow velocity.