A nucleotide is ?

Hint: Nucleotides are basic building blocks of nucleic acid consisting of a nitrogen base, phosphate group and sugar.

Complete answer:
Nucleotide consists of a nucleoside and a phosphate. nucleosides consist of a nitrogen base and sugar combined together.
These form the monomeric units of nucleic acids in DNA and RNA. Both DNA and RNA are essential in biomolecules with life forms.
a nucleotide consists of three subunit molecules: a phosphate group, nitrogenous base and a sugar. Phosphate group includes one to three groups. The phosphate group forms the backbone of DNA or RNA is also known as phosphate backbone.
The sugar is always the same, the only difference is between DNA and RNA. 5-carbon sugar can be deoxy in case of DNA and ribose in case of RNA. This gives genetic molecules their name.
In the case of DNA the nitrogenous base has two types pyrimidine (cytosine and thymine) and purine (adenine and guanine). DNA consists of cytosine adenine guanine and thymine. In RNA thymine is replaced by uracil.
Nucleotide has a simple structure which forms a complex DNA. DNA consists of two strands which are held together by hydrogen bonds.
Guanine and cytosine are held together by two hydrogen bonds and adenine and thymine consists of three hydrogen bonds.

Note:
Nucleotides play a major role in metabolism and provide chemical energy in the form of ATP GTP through cellular processes such as glycolysis Krebs cycle. It is also helpful in cell signalling cell metabolism and enzyme reactions