**Janus kinase** (**JAK**) is a family of intracellular, [non-receptor tyrosine kinases](https://en.wikipedia.org/wiki/Non-receptor_tyrosine_kinase "Non-receptor tyrosine kinase") that transduce [cytokine](https://en.wikipedia.org/wiki/Cytokine "Cytokine")-mediated signals via the [JAK-STAT pathway](https://en.wikipedia.org/wiki/JAK-STAT_pathway "JAK-STAT pathway")