h9

H9 is a numeric-alphabetic designation used in multiple fields to identify unrelated items that share the same label. As a code, it appears in biology, virology, and various product naming schemes. Because it is not a single entity, the meaning of H9 depends on the scientific or practical context in which it is used.

In biology and medicine, H9 most commonly refers to a human embryonic stem cell line used as a general model for pluripotency and differentiation studies. The H9 line is derived from the inner cell mass of a blastocyst and is widely cited in research on development, disease modeling, and regenerative medicine. It is sometimes labeled WA09 in cell repositories. H9 cells are typically maintained on defined substrates with specific growth factors and require validation of pluripotency markers such as Oct4, Nanog, and Sox2.

In virology, H9 denotes a hemagglutinin subtype of influenza A viruses. H9 subtypes circulate in avian populations and have been isolated from birds worldwide; H9N2 is a common and well-studied combination that has occasionally caused human infections. Monitoring of H9 strains focuses on mutations that could alter host range, transmission, or pathogenicity, and is part of broader influenza surveillance efforts.

Beyond science, H9 also appears in various product codes, model numbers, or route designations, and its precise meaning is determined by the associated system or organization.