State clearly what are known as nucleotides and nucleosides.

Explanation

### Step-by-Step Solution:

1. **Definition of Nucleosides**:
- Nucleosides are compounds formed by the union of a pentose sugar and a nitrogenous base.
- The pentose sugar can be either ribose (in RNA) or deoxyribose (in DNA).
- The nitrogenous base can be one of the following: adenine (A), guanine (G), cytosine (C), thymine (T), or uracil (U).

2. **Structure of Nucleosides**:
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