penetrable

Penetrable is an adjective describing something that can be penetrated or entered by another object, substance, or force. It can refer to physical intrusion, such as a material that a projectile can pass through, or to the passage of liquids, gases, or signals through a barrier. The term is commonly contrasted with impenetrable or impervious, which describe barriers resistant to penetration under given conditions.

In materials science and engineering, penetrability describes how easily a barrier can be crossed by a penetrant. Factors that influence penetrability include porosity, pore size distribution, thickness, and the driving forces involved, such as pressure gradients, diffusion coefficients, or mechanical stress. Materials may be selectively penetrable, allowing certain species to pass while blocking others.

In biology and medicine, penetrability relates to membranes, tissues, or barriers that permit or restrict transport of molecules. Transport can occur by diffusion, facilitated diffusion, active transport, or endocytosis, depending on molecular size, charge, and polarity. Permeability and selectivity are often used alongside penetrability to describe how barriers interact with specific substances.

In geology and hydrology, penetrability is related to the concept of permeability, an intrinsic property that governs the flow of fluids through a medium. A barrier is considered penetrable to water or other fluids if connected pore spaces and channels permit movement under a given hydraulic gradient. In security or information technology, the term can describe systems or networks that are vulnerable to unauthorized access or intrusion.

Etymology follows Latin penetrabilis, from penetrare to penetrate, with usage dating to early modern English. Related terms include permeable, permeability, and impenetrable.