"They live for eighteen months."

Translation: Sie leben achtzehn Monate.

[zongaspider]

How atypical/strange would it be to say für in this sentence?

i.e. Sie leben für achtzehn Monate

[NikolaSchildberg]

When is it "Monaten"? Is it when we have accusative and dative?
And is it a weak noun?

[MatthijsKo18]

Wikipedia says: ʿNouns in plural that do not already end in -n or -s (the latter mostly found in loanwords) gain an -n in the dative case. e.g. der Berg, die Berge, den Bergen.ʾ

https://en.m.wikipedia.org/wiki/German_declension#Nouns

[syonara123]

I would like to know this too

[ahh_bueno]

Only if it is plural dative

https://de.m.wiktionary.org/wiki/Monat

[HashishShetty]

"Monaten" when it's plural preceded by a dative preposition; e.g., Ich wohne seit drei Monaten hier. And AFAIK, it's not a weak noun.

[5tk96]

Can someone explain why the sentence is in this way? Why für is missing?

[Morgz6908]

Why not 'Wohnen'. We don't know the context of this sentance.

[PatriciaJH]

No. The English sentence doesn't mean "they reside for eighteen months."

[Eight81]

Could this sentence be used for talking about someone with a disease, to say they only have eighteen months to live?

[mainad]

You'd say that the same way in German: "Sie haben nur noch 18 Monate zu leben."

[bkerdan]

Sie leben 18 Monate LANG should also be correct

[PradeeshKa]

Why not Achtzehn monate leben sie ?