Early Quenya
yakse
noun. steel
yakse
noun. cow
akse
noun. steel
yaksi
noun. cow
aksina
adjective. steel
mui
noun. cow
yaisa
noun. steel
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
The noun ᴱQ. yaksi “cow” appeared in the Qenya Lexicon of the 1910s as a derivative of the early root ᴱ√Ẏak “a head of cattle” (QL/105). The contemporaneous Gnomish Lexicon also had ᴱQ. yaksi, but this form was deleted and ᴱQ. yakse was given as the cognate of G. gach “milch cow” (GL/36).
Conceptual Development: In Early Qenya Word-lists of the 1920s, the word for “cow” was ᴱQ. mui (PE16/132), likely related to G. mûs “cow” from the Gnomish Lexicon of the 1910s which had a deleted variant {mui} (GL/58). This probable relationship was suggested by Patrick Wynne and Christopher Gilson (PE16/132).
Neo-Quenya: For purposes of Neo-Quenya, I would adapt this word as ᴺQ. yaxë from the Neo-Root ᴺ√GYAK; Helge Fauskanger used this word for “cow” in his NQNT (NQNT).