Haploid-sufficient genes, also known as haplosufficient genes, refer to genes that require only one functional copy to maintain normal cellular function. These genes are critical for the survival and development of organisms, and their loss or mutation can lead to genetic disorders or even embryonic lethality. Synonyms for haploid-sufficient genes include haploinsufficient genes, genes with dosage sensitivity, and genes with haploessentiality. These terms all refer to genes that exhibit a critical threshold for expression or dosage, and require a certain amount of gene product for normal cellular function. Understanding haploid-sufficient genes and their synonyms is crucial for studying genetic diseases and developing therapies to treat them.