"This chair is too small."

Translation: Dieser Stuhl ist zu klein.

[Ashley94574]

Why is it 'dieser Stuhl' instead of 'dies Stuhl'?

[relox84]

When dies is used before a noun, it gets an additional ending which is the ending of the corresponding definite article:

der Stuhl -> dieser Stuhl

die Tür -> diese Tür

das Kleid -> dieses Kleid

die Leute -> diese Leute

[Asallam_Sensei]

thanks dude or girl

[Bill514919]

I really appreciate this explanation since I've been confused by similar usages on numerous occasions. I don't recall of Duo teaching us this.

[Luca894144]

Thanks for thorough explanation

[Filippo_84]

nice one, thanks

[Fan_von_Wien]

Thank you relox84 I understand that. However I don't understand what is Dative about this sentence.

[zeus36]

Nothing dative here and that's the point.
See, "zu" is one of the dative prepositions (which is what this lesson is about) but it isn't used as a preposition here in this sentence and Duolingo is trying to teach you that it also means "too" and not to confuse it with "zu" the dative preposition.

Basically, Duolingo is telling you to pay attention to the different usage of "zu" and not to always treat it as a dative preposition; hence, you don't trigger the dative case.

[relox84]

Nothing is in dative here: "dieser Stuhl" is nominative, dative would be "diesem Stuhl"

[-Ivngodoy]

Warum ist nicht Dieser Stuhl ist sehr klein?