A word for “child” derived from the root √KHIN (PE17/157; WJ/403), most notably an element in Eruhíni “Children of God”, a term for Elves and Men as the children of Eru. This word illustrates that hína has an abnormal plural form: híni rather than the expected ✱✱hínar. A variant hina with a short i was “only used in the vocative addressing a (young) child, especially in hinya (< hinanya) ‘my child’ (WJ/403)”.
Conceptual Development: The term Êruhîn “Children of God” first appeared as an Adûnaic word in the 1940s (SD/247-8, 358), later adapted as Quenya Eruhíni and Sindarin Eruchîn, which seems to be the source of Q. hína and S. hên “child”. At one point Tolkien coined masculine and feminine variants Q. hindo and Q. hindë, but they were deleted (PE17/157). Tolkien occasionally used an alternate Quenya form sén (MR/423; UT/274), perhaps out of a desire to have a Sindarin form Eruhîn that was closer to the original Adûnaic form; this variant continued to appear as late as 1969, where sén was written below Eruhíni as a variant form in Late Notes on Verbs (LVS: PE22/158).
hína noun "child", also hina used in the vocative to a (young) child (also hinya "my child", for hinanya) (WJ:403). Pl. híni (surprisingly not **hínar) in Híni Ilúvataro "Children of Ilúvatar" (Silmarillion Index); dative hínin in VT44:35. In compounds -hin pl. -híni (as in Eruhíni, "Children of Eru", SA:híni). According to one source, the word is hín(i) and solely plural (PE17:157), but this is obviously contradicted by some of the sources quoted above.