RNA, or ribonucleic acid, is a nucleic acid that plays a crucial role in protein synthesis and other cellular processes. It's made up of three main parts:

1. Sugar: The sugar component of RNA is ribose, a five-carbon sugar. This distinguishes RNA from DNA, which contains deoxyribose sugar.

2. Phosphate group: A phosphate group is attached to the 5' carbon of the ribose sugar. This forms the backbone of the RNA molecule, linking the nucleotides together.

3. Nitrogenous base: There are four main types of nitrogenous bases found in RNA:

* Adenine (A)

* Guanine (G)

* Cytosine (C)

* Uracil (U)

These bases are attached to the 1' carbon of the ribose sugar. Adenine pairs with uracil (A-U), and guanine pairs with cytosine (G-C), just like in DNA.

To summarize:

* RNA is a polymer composed of nucleotides.

* Each nucleotide consists of a ribose sugar, a phosphate group, and a nitrogenous base.

Remember that while these three parts are the fundamental building blocks of RNA, different types of RNA (like mRNA, tRNA, and rRNA) have unique structures and functions.