That's the problem with the lack of macrons and apices, here.
ōs = mouth,. (as in "per os"), gave oral from its genitive oris.
And also, second meanings: "face", "facial expression",
And also: voice, word, language, tongue, pronunciation, tongue
For bones, there are two words ŏs, neuter (genitive: Ossis, plural accu ossa) And ossum (genitive: Ossī, plural accu. ossa): neuter.
Second meanings: entrails, stone of fruit/the hard part of something, Sobriety. Skinniness.
Ossă = feminine. A Thessalia mountain.
It's the reason why macrons and apices become optional once you are not a beginner anymore, but are crucial to beginners.
If you pronounce "os" and "os" the same, you are wrong.
I agree with you about the desirability of including macrons, PN. However: 1) the English antonym of "macron" is not "apex" but "breve"; and 2) there is no need to use breves, since the absence of a macron (where they are used) is -- by default -- an indication of short vowel length. (I refer you to le rasoir d'Ockham.)
As said by Mosfet (I saw it later)
It can be the (nominative) word Ossum,
The (nominative) word Os
As they have both their acc. plural in "Ossa".
Os is a popular variant, and gave directly the French "os". (bone/bones).
I think French is not the closest language from Latin, but maybe one of the closest from popular Latin, or vulgar Latin.
When the Spanish and the Italian seems rather from Ossum (Spanish: hueso), (Italian: Osso)