A methylene radical is a chemical entity consisting of a carbon atom and two hydrogen atoms, having an unpaired electron. Synonyms for a methylene radical include carbyl radical, methanediyl radical, and methylene group. The carbyl radical is a term used in organic chemistry, whereas the term methanediyl radical is used mainly in inorganic and bioinorganic chemistry. The term methylene group is commonly used in organic chemistry to describe a functional group consisting of a single carbon atom bonded to two hydrogen atoms. These terms are often used interchangeably to refer to the same type of chemical entity. Understanding the synonyms for methylene radical is important for communication among chemists and can help in the understanding of various chemical reactions.