What is the definition of relative humidity?

Relative humidity is a critical concept in understanding how moisture content in the air interacts with temperature. It is defined as the percentage of water vapor present in the air compared to the maximum amount of water vapor the air can hold at a given temperature. This means that relative humidity reflects how close the air is to being saturated with moisture.

When temperatures rise, the air can hold more moisture, which means that relative humidity can change significantly with temperature variations. A high relative humidity indicates more moisture in the air relative to its capacity, which can affect comfort levels and the potential for condensation or mold growth.

While other options address aspects of humidity or temperature, they lack the specific focus on the relationship between current water vapor levels and the maximum capacity at a given temperature that defines relative humidity. Thus, the correct answer captures the essence of how relative humidity is understood and measured in conjunction with temperature.