A word appearing as ᴱQ. mildi “pease” in the Qenya Lexicon of the 1910s derived from primitive ᴱ✶mldẏǝ under the early root ᴱ√MLŘL [MḶÐḶ] (QL/62), where “pease” is an archaic word for “pea”. Tolkien somewhat cryptically said it was “used plural or as yə sing”. I interpret this to mean that it could be used as a collective plural form, or as a singular with stem mildy-. Tolkien could have been indicating that its singular *milde was a back formation from its apparently plural form mildi, much how English “pea” was derived from apparently plural “pease”, originally from Latin “pisa”.

Neo-Quenya: I would adapt this word as ᴺQ. mildë (mildi-) “pea” for purposes of Neo-Quenya.