penetrations

Penetration is the act or process of entering, piercing, or passing through a barrier or surface. Penetrations are openings, breaches, or the depth that an object or substance reaches within a material or system. The term is used across many disciplines to describe how far something can go, how something enters, or how a barrier is breached.

In physics and materials science, penetration depth or range describes how far a particle, wave, or radiation can travel into a material before it is absorbed or scattered. Examples include electron, ion, neutron, or photon penetration depths, which influence shielding design, imaging contrast, and processing parameters in semiconductor fabrication and other technologies.

In engineering and construction, penetrations are openings made to route pipes, cables, vents, or ducts through walls, floors, or ceilings. They require careful detailing to preserve structural integrity, fire resistance, and airtight or watertight performance, often using seals and fire-stopping materials to control leakage and maintain safety.

In biology and medicine, penetration can describe the movement of substances into tissues or cells, such as how drug molecules cross membranes or how imaging and therapeutic agents are delivered at the cellular level. It also relates to the ability of pathogens or other agents to breach protective barriers, with emphasis on mechanisms and clinical implications.

In security and information technology, penetration testing assesses a system’s defenses by simulating attacks under controlled conditions. Penetrations in this context denote successful or attempted breaches used to identify vulnerabilities and guide remediation, rather than illicit activity.