"Nucleobases" are the building blocks of DNA and RNA. These are the nitrogenous bases found in nucleotides, which make up the genetic code. There are four types of nucleobases in DNA-adenine, guanine, cytosine, and thymine. RNA, on the other hand, contains uracil instead of thymine. Although "nucleobases" is the most commonly used term, there are other synonyms that can be used interchangeably. These include nitrogenous bases, nucleotides, nucleic acid bases, or simply, bases. Each of these synonyms refers to the same chemical compounds that make up the genetic code and are essential for life as we know it.