sterile

Sterile describes a state in which a material, object, or environment is free from viable microorganisms, including bacteria, fungi, and their spores. In many contexts, the term implies that no living organisms capable of replication remain; viruses are not always considered alive, but in sterilization practice many standards aim to remove all viable forms regardless. Sterility is often characterized by a sterility assurance level (SAL), a probabilistic measure used in manufacturing and healthcare; an SAL of 10^-6 indicates fewer than one viable microorganism in one million items.

The word sterility comes from the Latin sterilis, meaning barren.

In medical and laboratory work, sterile technique provides a sterile field and uses sterile equipment to prevent contamination during surgeries, injections, or culture work. A related concept, aseptic technique, also aims to prevent contamination but does not guarantee absolute sterility; it focuses on minimizing the introduction of microorganisms.

Sterilization methods commonly used to achieve sterility include steam sterilization (autoclaving), dry heat, ethylene oxide gas, hydrogen peroxide plasma, and radiation (gamma rays or electron beam). For heat-sensitive items, high-level liquid chemical sterilants may be used, and sterile filtration can be employed for certain liquids to remove microorganisms when heat methods are unsuitable. The effectiveness of sterilization is verified by validated processes and packaging integrity, often described by a stated sterility assurance level.

Applications span surgical instruments and implants, pharmaceutical products, laboratory culture media, and food or medical-device packaging. Sterile products are essential to patient safety and product quality, and the concept underpins regulations, quality systems, and risk assessments across healthcare and industry.