Nouns in the following categories are feminine:
A) All nouns ending in -in, which is added to the masculine form of  professions and nationalities to render the female of the species, e.g.die Lehrerin, die Philosophin, die Amerikanerin.
B) All nouns ending in -heit and -keit, all of which express abstract  concepts, e.g. die Gelegenheit (opportunity), die Gemütlichkeit  (cosiness).
C) All nouns ending in -ung, e.g. die Übung (exercise), die Zeitung (newspaper).
D) All nouns of French origin ending in -ie, -ik, -ion, e.g. die Biologie, die  Musik, die Station.
E) Those rivers that are not masculine (see 6.1.1.g) are feminine, never  neuter, e.g. die Donau (Danube), die Elbe, die Isar, die Oder, die  Weser; die Seine, die Themse (Thames).