Capillarity

noun (uncountable)

/ˌkæpɪˈlærɪti/

Capillarity (also capillary action) is the ability of a liquid to flow in narrow spaces — such as capillary tubes, soil pores, or plant xylem vessels — against or in addition to gravitational force, driven by the interplay of adhesion (liquid-to-solid attraction) and cohesion (liquid-to-liquid attraction) and surface tension. Water rises in a glass capillary tube because adhesion to glass exceeds cohesion between water molecules. Capillarity is the mechanism by which water and dissolved minerals ascend from roots to leaves in tall trees, and by which water moves through unsaturated soil — a principle applied in drip irrigation systems deployed across 5.1 million hectares under India's PMKSY (Pradhan Mantri Krishi Sinchayee Yojana).

✍️ Usage in a UPSC answer

The efficiency of drip irrigation under PMKSY depends critically on the capillarity of irrigated soils: loamy soils with optimal pore structure allow lateral water spreading by capillary action, reducing both water consumption and evaporative loss compared to flood irrigation.

Synonyms

capillary actioncapillary risesurface tension effectwickingimbibition (in soils/plants)

Antonyms

drainagepercolation (downward water movement)surface runoff

🌱 Word Family

capillary (noun/adjective), capillary action (noun phrase), capillary pressure (noun phrase), capillary rise (noun phrase)

🔡 Root

Latin capillaris = of or relating to hair; from capillus = hair (referring to hair-thin tubes)

📜 Etymology

From Latin capillaris (hair-like, relating to hair) and capillus (a hair), because the phenomenon was first studied in hair-thin (capillary) glass tubes. The Latin capillus may be related to caput (head). Leonardo da Vinci first observed capillary action in the 15th century, but the scientific explanation in terms of adhesion and surface tension was developed by Thomas Young and Pierre-Simon Laplace in the early 19th century. The English noun capillarity follows the French capillarité.

🧠 Memory Hook

Capillarity = capillus (hair) — capillary tubes are hair-thin, and liquid climbs up them. Think of a paintbrush absorbing water: the hair-like bristles (capillaris) suck liquid upward through capillarity. Thin as a hair, drawing water up — that is capillary action.

⚗️ General Science 📖 Seen in: Human Body Systems — Organ Systems, Ph...

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