What does capillarity mean?
Capillarity — more commonly known in everyday contexts as capillary action — is the physical process by which a liquid moves through narrow spaces, thin tubes, or porous materials without the assistance of external forces like pumps. It arises from the interplay of two effects: the cohesion of the liquid's own molecules (surface tension) and the adhesion between the liquid and the surfaces it contacts. When adhesion to a solid wall exceeds the liquid's internal cohesion, as with water in glass, the liquid climbs; when the reverse holds, as with mercury, it is depressed. Capillarity explains familiar phenomena such as a paper towel soaking up spilled water, oil creeping along a lamp wick, and groundwater rising through soil toward plant roots. It also plays a vital role alongside other forces in transporting sap through the fine vessels of plants. The word is formal and scientific, appearing mainly in physics, chemistry, agriculture, and biology.
nounThe phenomenon by which a liquid rises in, or is drawn through, a narrow tube or porous material owing to surface tension and the attraction between the liquid and the solid surfaces. It is the property responsible for water climbing a thin glass tube against gravity.
- (physics) The movement or rise of a liquid within narrow tubes or porous materials caused by surface tension and adhesion between the liquid and the solid.
"Water reaches the leaves of a tall tree partly because capillarity draws it upward through the narrow vessels of the xylem."
"Capillarity causes water to rise several centimetres up a fine glass tube placed in a dish."
"Farmers rely on capillarity when moisture wicks up from the water table through the soil to plant roots."
Rarely pluralised; the singular form is standard even when referring to multiple instances of the phenomenon.
"The textbook discussed the different capillarities observed in water and mercury."
Capillarity lets water defy gravity — it's how trees taller than any building drink from the ground without a single pump.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of capillarity
Capillarity derives ultimately from the Latin 'capillaris', meaning 'of or pertaining to hair', formed on 'capillus', the Latin word for a hair. The term entered English via the French 'capillarité', coined in connection with the early study of liquids rising in hair-thin tubes during the seventeenth and eighteenth centuries. It shares this root with 'capillary', which describes both hair-thin blood vessels and fine tubes generally.
Related word forms
How capillarity is actually used
A technical term used chiefly in physics, chemistry, soil science, and botany. In everyday writing, 'capillary action' is often preferred as the more accessible synonym; 'capillarity' itself carries a formal, scientific register.
Easily confused with capillarity
'Capillary' refers to a hair-thin blood vessel or tube (or something resembling one), while 'capillarity' is the physical phenomenon of liquid movement in such narrow spaces.