I keep getting them mixed up. When do I use geen and when do i use niet?
You can translate "geen" as "no" in English, and "niet" as "not".
For example: "I have no cats" - "Ik heb geen katten"
"I do not have the cat" - "Ik heb de kat niet"
As a general rule, whenever you want to negate a sentence in dutch which is talking about an object you always use "geen" unless you're talking about a specific object.
I am not a doctor = Ik ben geen arts
I am not that doctor = ik ben niet die arts
I don't have a cat = Ik heb geen kat
I don't have the cat = Ik heb de kat niet
No letters came yesterday = Geen brieven kwamen gisteren
Your letter didn't come yesterday = Jouw brief is gisteren niet gekomen
If you're an English speaker, you can think of it like this: If I COULD use "no" instead of "not" to make this sentence in English, then I SHOULD use "geen" instead of "niet" toi make it in Dutch.
Good explanation. But "Ik drink koffie," in english would be "I drink coffee," which would become "I do not drink coffee". So according to you thesis I cannot use "no" and must use niet. However the right statement in dutch as stated by @SaskiaDaan below is, "Ik drink geen koffie." What's your explanation on this? Enlighten me.
It is not possible to completely follow the translation of niet = not en geen = no. The rule as I gave below is complete: so no particle before the noun (no 'de/het') - GEEN, the particle 'een' before the noun - GEEN; no particle or 'een' before the noun but also a preposition - NIET and in all other cases NIET (as a teacher of Dutch forforeigners my students and I have tried a lot of examples with translating but it does not work)
Well, the first part of the thesis holds true. Coffee in your example is a reference to coffee in general, if you wanted to tell someone in dutch you weren't drinking a specific cup of coffee you would say:
Ik drink die coffee niet - I am not drinking that coffee
Also, you can say "I drink no coffee" in english, it's not idiomatic but it's gramatically correct. It's like you could say "I am no doctor" in English, but would normally say "I am not a doctor".
But anyways, the rule I posted is just the guideline I use, it's not meant to be a bulletproof statement without exceptions :)
In general Geen is used in combination with nouns.
Overview: Subject with 'een' or notinhg in front of it ---- use geen
ik heb EEN auto - ik heb geen auto; ik drink koffie - ik drink geen koffie.
BUT when there is a preposition before it: ---- use niet:
ik zit IN een auto - ik zit niet in een auto Ik houd VAN koffie - ik houd niet van koffie.
IN ALL OTHER CASES USE NIET