Which term describes a reduction in visibility caused by particles in the air?

The term that best describes a reduction in visibility caused by particles in the air is haze. Haze occurs when fine particles, such as dust, smoke, or other pollutants, are suspended in the atmosphere, scattering light and leading to a decrease in the clarity of the air. This can result in a noticeable reduction in visibility, especially during certain weather conditions.

The other terms do not fit this definition as precisely. For instance, sunny refers to clear weather with no clouds or visibility issues. Fog, while also leading to reduced visibility, is specifically caused by the condensation of water vapor in the air, resulting in tiny water droplets that lead to a thicker and more opaque obstruction. Clear indicates no obstructions to visibility, which is the opposite of the condition described. Hence, haze is the most accurate term for a situation where visibility is reduced due to particles suspended in the air.