Contiguous is an adjective that means “touching”, “adjacent”, or “near” – either physically or with respect to time.
It comes straight from the Latin word contiguus, a combination of com-, “together”, and tangere, “to touch”.
I like this word because of the overarching, fundamental concept it represents. Just take a look at Wikipedia’s page on Contiguity to see its specific meanings in different areas of study. It shows up in everything from physics to psychology!
But contiguous shows up most often in the phrase “the contiguous United States”, which refers to the 48 states “on the North American continent south of the border with Canada, plus the District of Columbia” (Wikipedia).