A word for “child” derived from the root √KHIN, more specifically from ✶khinā with short i which became e in Sindarin due to a-affection (WJ/403). It often appeared in its mutated plural form chîn in phrases like Narn i Chîn Húrin “Tale of the Children of Húrin” (WJ/160). This is pronounced with spirantal “ch” as in German Bach, not affricate “ch” as in English “church”.
Christopher Tolkien made the editorial decision to render this plural form as Hîn in The Silmarillion as published as well as in Unfinished Tales, where it “was improperly changed by me [Christopher Tolkien] to Narn i Hîn Húrin ... because I did not want Chîn to be pronounced like Modern English chin” (LR/322).
In the Quendi and Eldar (Q&E) essay of 1959-60, Tolkien said “S has hên, pl. hîn, mostly used as a prefix in patronymics or metronymics”, meaning this word was often used to mean “child of” in reference to one’s parents, for example Túrin hen-Chúrin [Húrin] or Túrin hen-Morwen [assuming nasal-mutation].
A neologism for “to follow” coined by Sami Paldanius in the VQP (VQP), derived from the root √KHIL of similar meaning. I prefer attested aphad- “follow”.