phycocyanin

This term is a specialized biochemical designation used primarily in microbiology, botany, and nutritional science. It describes a specific phycobiliprotein, and as such, it carries a neutral, technical connotation. It is almost exclusively encountered in academic papers, laboratory reports, or on the ingredient lists of health supplements derived from spirulina.

As a chemical compound and a specific protein complex, the word is treated as an uncountable mass noun. It refers to the substance itself rather than individual units of the pigment. Consequently, it does not have a plural form in standard scientific usage.