A word for “sister” in The Etymologies of the 1930s derived from the root ᴹ√THEL or THELES of the same meaning, with an irregular plural thelei (Ety/THEL). It had a more elaborate form muinthel, the equivalent of muindor “(dear) brother”, with an initial element muin “dear”.
Neo-Quenya: In notes from the late 1960s, Tolkien introduced a new word nethel for “sister” from the root √NETH (VT47/14). However, I think thêl and related words might be retained to mean a “metaphorical sister”, a close female associate who may or may not be related by blood, as with such words as gwathel “[sworn] sister, associate”. In this paradigm, I would assume muinthel still refers to a sister by blood, with an added connotation of strong affection. I think it’s best to assume the irregular Noldorin plural pattern was reformed to the normal Sindarin plural thîl.
A word for “sister” in The Etymologies of the 1930s derived from the root ᴹ√THEL or THELES of the same meaning, with an irregular plural thelei (Ety/THEL). It had a more elaborate form muinthel, the equivalent of muindor “(dear) brother”, with an initial element muin “dear”.
Neo-Quenya: In notes from the late 1960s, Tolkien introduced a new word nethel for “sister” from the root √NETH (VT47/14). However, I think thêl and related words might be retained to mean a “metaphorical sister”, a close female associate who may or may not be related by blood, as with such words as gwathel “[sworn] sister, associate”. In this paradigm, I would assume muinthel still refers to a sister by blood, with an added connotation of strong affection. I think it’s best to assume the irregular Noldorin plural pattern was reformed to the normal Sindarin plural thîl.