The essential parts of ANY noun are the 1) nominative singular, 2) the genitive singular, and 3) the nominative plural.
1. From there the FULL declension of ANY noun may be worked out.
2. It is necessary in German to know which case (Nominative, Accusative, Genitive or Dative ) of the noun is required.
3. with verbs which take a complement and not a direct object, that is to say verbs where the predicate is in fact the same as the subject, as in He seems a nice man, the complement will be in the nominative case, although in the position where English would expect the object.
eg. after the following verbs :