Leukemia inhibitory factor (LIF) is a protein that plays a critical role in the regulation of embryonic stem cells and the immune system. There are several synonyms for LIF, including leukocyte inhibitory factor, differentiation-stimulating factor, cholinergic differentiation factor, melanoma-derived LIF, and T-cell-derived LIF. While LIF was first identified for its ability to inhibit the growth of leukemia cells, it has since been shown to have a wide range of functions in the body, including promoting cell differentiation and survival, regulating fertility, and modulating the immune response. Understanding the synonyms for LIF is important for researchers, clinicians, and patients alike in order to accurately communicate about this important protein.