In food and medical contexts, sterile means completely free of living microorganisms — no bacteria, yeasts, moulds, viruses, or spores capable of growth. Sterility is the goal of processes such as canning, UHT treatment, and the aseptic packing of medical supplies, and it is verified by microbiological testing since it cannot be seen or tasted. The term is absolute: something is either sterile or it is not, though in practice sterility assurance levels express the statistical probability that an item is sterile. The word has a second, unrelated meaning in biology: unable to reproduce. For food manufacturers, achieving sterility in shelf-stable products is what allows them to be stored at room temperature for months.