When do you use nächste; and when do you use nächsten?

Also, why does an change die to der?   

Hi Anita,

The ending of "nächste" changes depending on the case that is used. German makes distinctions between cases in their adjectives and articles. For more information on cases please refer to the grammar chapter 14.6, 14.7 and 14.8 German Cases. 'Nächsten' can also be the plural form of 'nächste'. "Die Rentengelder der nächsten Generationen" = "The pension funds of the next generations".
The word "nächste" can be "der nächste" when used in conjunction with masculine, for example "Der nächste Tag" (The next day) with "Tag" being masculine or "die nächste Woche" (the next week), "Woche" being feminine. It can also be neuter "das nächste Abenteuer" (the next adventure), "Abenteuer" being neuter. 

"Nächste" can also be used as a noun, for example: "Der Nächste bitte!" or "Die Nächste bitte" translates to "Next one please!".
The plural form here would be "Die Nächsten bitte!" meaning "next group of people". 

Regards

Paul

This is the same question as I was going to ask but I still don't understand why "an" in German changes the Die to a Der.

Lesson 3.2: "...und an der nächste Ampel links"

Nik says that it is Die Ampel but it changes to a der... why is this?

Danke

Hi Annita and Darren,

I think I can answer that. 'Die Ampel' is the nominative case, i.e. Ampel is the subject.  A preposition such as 'an' changes the case of the article from nominative to either dative or accusative i.e.a direct or indirect object of some action.   Some prepositions are always dative while others are always accusatative.  Some can be either depending on the usage. 'An' is one such two way preposition.  The rules for whether a two way preposition is dative or accusative are a little subtle and appear to be motion oriented.  The following link describes it in more detail. http://german.about.com/library/blcase_dat2.htm
 

Thanks Byron - guess I have much to learn about the English language along this road to learning German. Dative/Accusative etc....never even heard of this before!

You'll get to it later on in your lessons.  Rocket, wisely I think, doesn't try to give you all the grammar rules upfront.  That's old school and about the best way to discourage a student from ever learning a new language.  German grammar is a bit more complicated than English in my opinion.  English has cases too that affect the pronoun used but not the article.  And the gender!  But don't worry about it.  Have fun learning.  If you get the gender or case wrong, no big deal.  

Hey Darren and Byron,

You are right Byron. Germans will still understand you. It is already difficult enough learning articles in German when you're coming from a Language that only has 'the' for singular, plural and all genders disregarding understanding how the cases change the articles.

 Examples on how 'an' changes the article:
'Die Ample'- "...an der nächste Ampel links einbiegen" = "...turning left at the next traffic light " 
'Das Haus'- "...an dem (am) nächsten Haus links einbiegen" = "...turning left at the next house"
'Der Baum'- "...an dem (am) nächsten Baum links einbiegen" = "...turning left at the next tree."
'Die Bäume'-"..an den nächsten Bäumen links einbiegen" = "turning left at the next trees"