Oligonucleotides:

Sequence of a few to many hundreds of nucleotides, linked with each other. An oligonucleotide thus corresponds to a (very) short DNA single strand. 


Nucleotides:

The subunits of a DNA molecule 

Monomers of which DNA and RNA are built. They consist of phosphates, a nitrogenous base and a carbon chain. 

nitrogen-containing molecules which link together to form strands of DNA and RNA. 

Molecules composed of a nitrogen containing base, a 5-carbon sugar, and one or more phosphate groups. Long strands of nucleotides form nucleic acids (see above). The sequence of bases in DNA or RNA represents the genetic (hereditary) information of a living cell.