Why is it that in esperanto there is no word for "a" Like, a man is just viro.
Because it's more simple like that. There are many real languages without articles at all.
Like Russian, but only in certain things.
Most asian languages are like that. It is just like baby talk! SImple
What's the difference between "viro" and "viron"?
"viron" is the accusative of "viro" (object of a transitive verb).
Why is "la viro kaj la virino" incorrect?
Because "la" means "the". The translation doesn't ask for a definite article.
I see, I guess it is just habit I have from Spanish. Thank you.
I studied French for many years and I sometimes have that problem with Esperanto too :)
Is "dancas" the plural of "danca?"
No. "dancas" is the present of the verb "danci" (to dance).
You need to start reading the Tips & Notes: nouns are marked with -o ("dance" is danco, not danca) and plurals with -j (dancoj, "dances").
What is the rule for plurals?
Add a -j at the end of a noun. e.g. viroj is men
why "a man" is only "viro" and not "la viro"?
"La viro" would mean "the man". La is a definite article. Esperanto doesn't have a word for indefinite articles, so instead of saying "a man" like in English, you just say "viro".
Why not unu viro kaj unu virino dancas? One may want to stress that there are only one man and one woman dancing?
One may, but that's not the meaning here.