Here's why:

* Nucleic acids are large biomolecules essential for all known forms of life.

* They are composed of long chains of repeating units called nucleotides.

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

* DNA and RNA differ in their sugar component (deoxyribose in DNA, ribose in RNA) and one of their nitrogenous bases (thymine in DNA, uracil in RNA).

So, while DNA and RNA have different structures and functions, they both fall under the umbrella term "nucleic acids."