So if I recall Tom you are familiar with Greek so I am not really educating you but I am still going to do the explanation to explain my thought process. Also this can be educational for other readers.

J the letter in latinized alphabets (collection of 26ish letters) is a recent development.

J originally had an Y sound, yet was written with the i and I symbol

But since the letter I can have different sounds when it is used as a vowel vs a constant they started using a new symbol to represent this sound which was the letter j / J. I need to look this up but if I recall it is only a recent 500 year old development, wikipedia confirms the 500 year history but I know wikipedia can often be overly simplistic with some subjects such as language for there are not brightline instant transformations where everybody suddenly agrees on the new way to spell or pronounce things.

The sound for J though begins to change, originall it was a Y sound like Yet and Jet, but due to English taking so many words from French and that France has a different pronunciation of J we get the modern pronunciation over time of J.

Thus words like YHWH with a Y sound eventually becomes some form of bastardization that is Yehowah or ΙΕΗΩΟΥΑ that is then bastardize into IEHOVA and then bastardize into Jehovah (and don't you dare have disdain and make snide remarks when you correct me for the steps one word over 2500+ years is then converted into Modern English with at least 2 language intermediaries in between the English to Hebrew with Greek and Latin. Feel free to correct me but do be snide when you do so)

Similar stuff for the Letter / Symbol Y. Y did not have a letter or a sound originally in latin but it was used in Greek and thus they sometimes used the I symbol and called it the Greek version of I. Eventually Y was added to Latin, but was rarely ever used and only used effectively for loanwords. Now the Y symbol was added to English but we have 5+ sounds that Y can make for there are other places we take how to pronounce it and the words that we derive from it.

Now I been talking about spelling, phonetics, and the evolution of language. Well Grammar is much the same thing. Language changes over time Tom, what we have about languages that are PIE in origin (proto indo european) that used to be something close to 1 language but over time the language evolved and you got very different rules of pronunciation and grammar. PIE is older than spelling (with a phoenician based alphabet by several thousands years) and writting (by about a 1000 years) with most estimates now a day saying probably 6,000 years old if what happened to PIE was the Kurgan Region / Yamna Culture hypothesis or it could be even older if Anatolian Hypothesis turns out to be true (probably about 8,000 years). That said the history of PIE is constantly being challenged every year.

What makes language and language rules authoritative? If people do not agree with the authority and it is just rules that are not tethered to a common agreement between people then language will always change.

Language has legitimacy (not authority). Now when I say authority I am referring to the originator aka the latin word auctor version of authority. Aka who is the original, the prototype, the zero where bind the axis. If we can't find an original author, or people do not accept this author as the one and only then what we really have is a stand alone complex, a situation where we can't tell the difference between a simulacra and the original / the prototype / the archetype. There is no ideal, there is no authority, their is only legitimacy for language is used not to describe prime essences but instead used for its mixed states or only used for its utility.

It is a pompous and wieldy work that could have been better written but Plato was right in one of his later works that is Philebus. Mathematics (which can have purely imaginary concepts) vs Physics (testable stuff in the real world) are both not the greater good, but only when you mixed the two can you reach the maximum happiness. In fact it is not even the mixed states but once we can take a mixed state and turn into into an abstraction that brings utility that we get maximum happiness for we are now organizing nature by capturing the important parts and abstracting the rest and this is what reason at its core is. It is a form of creation.

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Sigh I hate these perfectionistic dialogues that sometimes people do with mathematics, language, and other subjects where they seek for purity. Seriously it just feels so unremoved from the real world...it feels like someone is going completely OCD and missing the point. The gaining of knowledge and not caring about the real world and instead seeking purity is just an individual trying to create a geocentric model of the universe. Well the universe is not geocentric, nor is it individualistic. The universe is relational but their is no form of absolute relation, or objective form of relation but instead relative form of relation.