1. A nitrogenous base: This is a molecule with a nitrogen-containing ring structure. There are five main types: adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U).

2. A five-carbon sugar: This is a pentose sugar, either ribose or deoxyribose.

3. A phosphate group: This is a molecule containing phosphorus and oxygen.

These three components are linked together in a specific way: the nitrogenous base is attached to the sugar, and the phosphate group is attached to the sugar.