"The coach wants the first horse."
Translation:Der Trainer will das erste Pferd.
Because "das" is already carrying the gender mark. In this case, adjectives take only an "-e" ending: "der große Hund"; "das starke Pferd"; "die süße Katze".
With determiners that are ambiguous relative to gender ("ein" or "mein", for instance, can be either masculine or neuter), you need the adjective to take the gender ending: "ein großer Hund"; "mein starkes Pferd".
Mas, Neu, Fem, Plu Nom: e-e-e-en Akk: en-e-e-en Dat: en-en-en-en Gen: en-en-en-en
Read a grammar book. Duo won't teach you that.
there are three different tables for adjective inflection in German (called strong, weak and mixed). Which one is applied depends on whether there is a definite article present (-> weak), an indefinite one or a possessive pronoun (-> mixed) or no article (strong).
So in "my first child/horse" you have to look up the form in the mixed table, resulting in "mein erstes Kind/Pferd", whereas "the first child/horse" needs the weak table, resulting in "das erste Kind/Pferd".
Step 1) Identify: case, gender/number, preceding article (if any).
- Case = accusative (for case explanation, see link below)
- Gender or Number = neuter (das Pferd) and singular (das not die, and Pferd not Pferde)
- Preceding article = "das" (a definite article) not "ein" (an indefinite article) or possessive pronoun etc...
Step 2) Find appropriate ending in the chart you memorized earlier. What's that? You didn't memorize it yet? Well, here it is (and others): http://en.wikipedia.org/wiki/German_declension#Weak_inflection.5B6.5D.5B7.5D
*Case explanation if you need it: http://coerll.utexas.edu/gg/gr/cas_01.html
I suggest you bookmark the first link, or print out the charts. They will help answer a lot of your Duolingo questions. Hope that helps!