= Bent molecular geometry
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In <bent molecular geometry>, two neighbours and their central <chemical atom> form a noncollinear <triangle>, with an interior <bond angle> strictly between $0^\circ$ and $180^\circ$. <Water>, $\mathrm H_2\mathrm O$, is the standard example. The https://cccbdb.nist.gov/exp2x.asp?casno=7732185&charge=0[NIST CCCBDB experimental water entry, internal coordinates, citing Hoy and Bunker (1979)] gives the equilibrium H–O–H <bond angle> as $104.4776^\circ$ with quoted uncertainty $0.0019^\circ$, usually rounded to $104.5^\circ$.
The <oxygen> in <water> has two bonding <electron domains> and two <lone pairs>. Its ideal <electron pair geometry> is tetrahedral, while the three <atomic nuclei> give <bent molecular geometry>. Three points always lie in a plane; this does not make the four-domain scaffold planar. Nor does the word bent by itself determine an <electron domain> count: the same atomic shape can arise from other domain arrangements.
In an illustrative model with two equal bond-dipole contributions of magnitude $p$ separated by <bond angle> $\theta$, their sum of <vectors> points along the bisector and has magnitude $2p\cos(\theta/2)$. At $180^\circ$ it vanishes; at $104.4776^\circ$ it is approximately $1.2247p$. This ratio is a geometric calculation, not a prediction of <water>'s measured <electric dipole moment>. The entire <electron density>, including contributions represented by <lone pairs>, matters. <Water> is a <polar molecule>; <chemical polarity> helps explain its interactions with other <polar molecules>. See https://openstax.org/books/organic-chemistry/pages/2-2-polar-covalent-bonds-and-dipole-moments[McMurry, Organic Chemistry, §2.2: water, lone-pair contributions, and polarity].
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