A single-copy gene is a term used to describe a gene that exists as a single functional copy within an organism's genome. However, there are several synonyms that can be used to refer to this type of gene. For example, it may be referred to as a "unique gene," "monogenic," or "non-duplicated gene." Other synonyms may include "singleton gene," "haplosufficient gene," or "parental gene." The use of synonyms allows for more variety in language and can be helpful when discussing genetic research or biology. Ultimately, the use of such synonyms helps to broaden an individual's understanding of genetic terminology.