"I will not buy chairs."
Both いすはかいません and いすをかいません are correct. They essentially mean the same thing.
The difference is いすをかいません is "I will not buy chairs" and いすはかいません is more like "I will not buy CHAIRS" (though less emphatic.) は is a subject marker and を is an object marker. By putting the subject marker instead of the object marker on "chairs", you put a certain emphasis on it.
I'm a native Japanese speaker and have never studied Japanese grammar. Sorry if my explanation doesn't make a lot of sense, this is merely how I (and how I think other Japanese speakers) interpret things.
"Subject" is a grammatical term for what is marked in Japanese by が. は is called "topic marker".
No, because が is for the grammatical subject, the one doing the action. いすがかいません would mean "chairs will not buy (me)".
Man,dont you hate it when your a chair buying addict and you gotta tell your self "いすはかいません"
Is "いすたちは買いません" correct ? Because Duo refused my answer. I can't tell if it's because of the plural suffix たち or if I wasn't supposed to use the kanji form of the verb 買 ( to buy, かう)
I was also wondering why this is plural in this example, whereas in the 'table' example, it's singular
Because you usually only need one table. If there is no number specified, then singular or plural is implied by context.