What is example of a base in science?

In chemistry, a base is a substance that typically will have a pH greater than 7 in an aqeuous solution. The opposite of an acid. It typically will accept a proton (H+).

In biology, a base may be a basic building block: in the DNA molecule, you have a specific base-pairing, which consists of a a sugar and phosphate. In the DNA molecule, the base A (adenine) bonds with T (thymine), while C (cytosine) binds with G (guanine)