I just barely understand the gist of what you are saying. Not a criticism, just saying 'have pity'!
Haha no worries!
Basically a concordance tells you what English word the Greek was translated into and where to find.
A lexicon will often provide a more comprehensive definition, and assign verses to said definition.
So for example, thayer’s lexicon lists several definitions for genea: birth, family of same stock, multitude living at the same time, and age. Thayers assigns Matthew 24:34 to the definition “multitude living at the same time”. Matthew 24:34 is not listed under any other definition. Thus thayers states it means “multitude living at the same time” in the context of Matthew 24:34.
However, if you use thayer’s lexicon to argue genea in Matthew 24:34 should mean family of same stock, you are using thayer’s incorrectly, as Thayer does not list Matthew 24:34 under the definition family of same stock.
A word does not mean all of its definitions in every instance. In other words genea does not mean birth, family of same stock, multitude living at same time, and age in Matthew 24:34. Thayer has assigned genea Matthew 24:34 to “multitude living at same time”. However, if you were to select another definition from thayers to apply, like family of same stock, because you don’t like how thayer’s assigned genea in Matthew 24:34, that would be the fallacy of illegitimate totality transfer.
This is not to prove that thayers is the ultimate authority of what genea means in Matthew 24:34. It’s only to demonstrate the correct way to use thayers.