Proximity means nearness or closeness to something. When your house is in close proximity to your school, you live near enough to walk there easily. When a weather forecaster talks about a storm's proximity to the coast, she means how close the storm is to reaching land.

The word works for physical distance, like when a park ranger warns hikers about the proximity of bears in the area. But it also describes other kinds of closeness. Scientists studying disease might investigate the proximity of contaminated water sources to neighborhoods with health problems. Archaeologists get excited when they discover artifacts in close proximity to each other because items found near each other can tell connected stories about how ancient people lived.

You might hear someone say they chose an apartment because of its proximity to public transportation, or that a witness's proximity to an event made their testimony especially valuable. The word has a more formal, precise feel than simply saying “nearness” or “closeness.” When proximity matters enough to measure or discuss carefully, that's usually when people reach for this particular word rather than just saying something is “close” or “nearby.”