Grammatical Analysis
Āpodhātu: [f.] water element; element of cohesion; fluidity. Formed by āpo (water, liquid) + dhātu (element).
Orthodox Definition
Āpodhātu is the second of the four great physical elements (mahābhūta). Rather than literal water, it represents the abstract material principle of cohesion, binding, and fluidity.
The commentaries state that its characteristic is trickling or oozing (paggharaṇa-lakkhaṇā), and its primary function is to intensify or bind material particles together (āyūhana-rasā or saṅgaha-rasā). Without the water element, the earth element (solidity) would crumble into disconnected dust; āpo provides the magnetic-like cohesion that holds physical shapes intact.
Unlike the other three great elements, the water element cannot be directly felt by the body-sense (kāyāyatana); one can feel the pressure (wind), the temperature (fire), or the hardness (earth) of literal water, but the pure cohesive element itself is known only through mental inference (mano-viññāṇa). Internally, it manifests predominantly as bodily fluids: bile, phlegm, pus, blood, sweat, fat, tears, saliva, and urine.
Textual References
- Sutta: Rāhulovāda Sutta (MN 62) – The Buddha instructing Rāhula to meditate like water, which receives both clean and foul things without aversion.
- Abhidhamma: Dhammasaṅgaṇī (Rūpakaṇḍa).
- Commentary: Visuddhimagga (Chapter XI) – Defining the abstract cohesive properties of matter.