N-acetylneuraminic acid, often abbreviated as Neu5Ac, is a type of sialic acid, a family of nine-carbon sugars. It is commonly found on the surface of cells in animals and plays a crucial role in various biological processes, including cell recognition and signaling. Neu5Ac is important for immune response and is involved in the development of the nervous system. This compound is also significant in the study of viruses, as many pathogens, including influenza and HIV, exploit sialic acids to attach to host cells. Understanding N-acetylneuraminic acid can help researchers develop vaccines and treatments for viral infections.