Is "sheep" singular or plural? To figure that out, you need to see it used in context, and understand that context. Compare:

• My sheep is woolly
• My sheep are woolly

If I have many people called "Edward", you can pluralise it by saying:

• There are many Edwards here

So can we then conclude that "James" is plural?

Then consider the -en plurals - children, men, women, Vaxen and so on. So "vixen" should be plural, right?

Basically, it can't be done without just encoding the dictionary.