kein, keine, keinen, keiner
These are the first words I've had problems with so far in the German course.
Is there a way to remember which is used in what sentence? Is there an easy way I'm missing?
To decide which one to use, you need to know the noun's gender. Kein etc declines identically to ein etc, just with a k- at the beginning.
Kein is used with masculine nouns in the nominative, and neuter nouns in the nominative and accusative. Keine is used with feminine and plural nouns in the nominative and accusative. Keinen is used with masculine nouns in the accusative. Keiner is used with plural nouns in the genitive and feminine nouns in the plural and genitive.
If it helps, this is a good chart for remembering (k)ein.
I know this is an old question, but this may help someone else. I just discovered there are two separate forms of kein-: 1) negative article and 2) indefinite pronoun! They have slightly different inflections.
If kein- comes before a noun, it's an article, like so: "Ich habe kein Auto."
If kein- takes the place of a noun, it's an indefinite pronoun, like so: "Hast du ein Auto? Nein, ich habe keines."
See? Different inflections referring to the same, neuter noun (Auto) in accusative case.
Needless to say, this was very confusing! Also beware the similar difference between ein and einer! https://www.deutschplus.net/en/pages/Indefinitpronomen_einer_keiner_welcher