Breakdown of Die Zielperson spricht nur mit einem Bekannten.
ein
a, an (eine)
sprechen
to speak
mit
with
nur
only
Questions & Answers about Die Zielperson spricht nur mit einem Bekannten.
Why does the word for acquaintance end in -en here (einem Bekannten)?
Bekannter is a nominalized adjective (an adjective acting as a noun). Just like a regular adjective, its ending changes based on the case and the article before it. The preposition mit forces the dative case. After the dative article einem, adjectives always take the -en ending.
How would we say the target person speaks with a female acquaintance?
It would be: Die Zielperson spricht nur mit einer Bekannten. The article changes to the feminine dative form (einer). The word Bekannten keeps the -en ending, because nominalized adjectives following a dative article always end in -en regardless of gender.
If this is a nominalized adjective, what original adjective does it come from?
It comes from bekannt, which means "known" or "familiar". So when you talk about an acquaintance in German, you are literally referring to "a known person".
The noun die Zielperson uses the feminine article. What if the target is a man?
It remains die Zielperson. In German compound nouns, the last word dictates the gender. Since die Person is always grammatically feminine, any word ending in -person is also feminine, regardless of the actual biological gender of the individual.