"The arrow killed the dragon."
Translation:Το βέλος σκότωσε τον δράκο.
Grammar rule for the ending "ν" (I have literally copy-pasted the rule from the 11-12 year olds' grammar book). :
The ending (final) "-ν" in the words "δεν, μην, την (article), αυτήν (or την) (personal pronoun in the accusative case)" DROPS when the following word starts with one of the GR laryngeal consonants (εξακολουθητικά σύμφωνα) "γ, β, δ, χ, φ, θ, μ, ν, λ, ρ, σ, ζ". The change obviously is from "δεν" > "δε", "μην" > "μη", "την" > "τη" and "αυτήν" > "αυτή".
The grammar rule basically states what comes natural when speaking the language. The current trend of adding a final "-ν" in the above words is unfortunately wrong and I believe started out in the past decade or less from people that wanted to sound more "upper class". It has indeed caught (mostly due to ignorance and the telly) but it is still wrong.
PS: Greek people do not generally believe in "upper class". The nation is so old it makes no sense to do so. They can of course be quite snobbish, just like anybody else, only they save their best and most elaborate mockery for the pretentious people ;-D.
This rule does not apply to τον in order not to be confused with the neutrum article το. (In written Greek) Spoken Greek may omit the -ν.
The rule doesn't apply also to the plural accusative case of the definite article (των), to the indefinite article ένας in the accusative case (έναν), to the personal pronoun αυτός in the accusative case (αυτόν strong type / τον weak type), and to the particle σαν when used to show similarity (σαν λύκος - like a wolf). In some rare cases when σαν is used as a conjunction showing time (meaning when, as soon as, or every time), there could be seen a type without the final -ν, but this occurs mostly in poetic speech. As mentioned above, these happen principally in written word. In speech the final -ν might be omitted.