"This chair is too small."
Translation:Dieser Stuhl ist zu klein.
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
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.
Thank you relox84 I understand that. However I don't understand what is Dative about this sentence.
Nothing is in dative here: "dieser Stuhl" is nominative, dative would be "diesem Stuhl"
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.