I do not see that as the only conclusion. Even the English language often uses the same word with different meanings dependent upon the context. The Biblical account of the six days of creation attache the word "one" to the word "day," where in 2:4 the word "one" is absent, much as when we say "back in the day" we do not mean a singular day, but an indefinite period of time.
So there is more than one conclusion to be drawn here. Frankly, mine makes more sense in light of the fact that it can be demonstrated from the history of language that the same word can often be used with different meanings depending on context.
You must be truly confused if you think the same word must have the same meaning every time it occurs in the Bible.
"YOM MEANS PERIOD in this context" is my conclusion. Yet you say:
"Even the English language often uses the same word with different meanings dependent upon the context."
Does morality ever enter into a creationist argument?