[ paw-ros-i-tee, poh-, puh- ]
/ pɔˈrɒs ɪ ti, poʊ-, pə- /

noun, plural po·ros·i·ties for 2.

the state or quality of being porous.
Geology, Engineering. the ratio, expressed as a percentage, of the volume of the pores or interstices of a substance, as a rock or rock stratum, to the total volume of the mass.

Origin of porosity

1350–1400; Middle English porosytee < Medieval Latin porōsitās. See porous, -ity

Word story

Porosity, “the state or quality of being porous or full of pores,” comes via Middle French and Old French porosité, porrosité from Medieval Latin porositās (stem porositāt- ), a derivative of the Medieval Latin adjective porōsus “porous,” itself a derivative of Late Latin porus “a passage, a channel in the body, an air passage.”
Porus is a borrowing of Greek póros “passage, ford, means, way out,” from the Proto-Indo-European root per-, por- (with other variants) “to lead, pass, pass over,” from which Latin derives portus “harbor” (from the sense “passage”) and portāre “to carry.” Proto-Indo-European por- becomes far- in Germanic, forming the verb faran “to wander,” Old English faran “to go, proceed, travel” (English fare ). From far-, Germanic also forms the verb farjan, Old English ferian “to carry, convey, transport” (English ferry ).
Both porous and porosity first appeared in a 14th-century English translation of a Latin encyclopedia of the sciences, an influential work that was written in the mid-13th century. The reference was to the tongue, described as being “porous and spongy.”
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for porosity

British Dictionary definitions for porosity


/ (pɔːˈrɒsɪtɪ) /

noun plural -ties

the state or condition of being porous
geology the ratio of the volume of space to the total volume of a rock

Word Origin for porosity

C14: from Medieval Latin porōsitās, from Late Latin porus pore ²
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for porosity


[ pə-rŏsĭ-tē, pô- ]


The state or property of being porous.
A structure or part that is porous.
A cavity or perforation.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for porosity


[ pə-rŏsĭ-tē, pô- ]

The condition of being porous.
The ratio of the volume of all the pores in a material to the volume of the whole.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.