Learn Hardcore German: Meine Schwester spricht mit leuchtenden Augen über ihre Leidenschaft für das Schreiben. - My sister talks with shining eyes about her passion for writing.

Idiomatic meaning: it describes someone who is talking with great enthusiasm, excitement, or passion. It suggests that her eyes are shining because she is so interested and emotionally involved in what she is talking about.

So the sentence implies not just that she speaks, but that she speaks very enthusiastically about her passion for writing.

Why is it mit leuchtenden Augen and not mit leuchtende Augen or mit leuchtender Augen?

Because of case and adjective endings:

The preposition mit always takes the dative case.
Augen is the plural of das Auge (eye).
Dative plural ending for adjectives with a determiner (like mit) is -en.

So:

Nominative plural: leuchtende Augen (shining eyes)
Dative plural (after mit): mit leuchtenden Augen

That’s why leuchtenden has -en: it’s an adjective in the dative plural.

What grammatical role does mit leuchtenden Augen play in the sentence?

Mit leuchtenden Augen is a prepositional phrase that functions as an adverbial of manner.

It answers the question How does she speak?
→ She speaks with shining eyes → enthusiastically / passionately.

So grammatically:

Subject: Meine Schwester
Verb: spricht
Adverbial of manner: mit leuchtenden Augen
Prepositional object (topic): über ihre Leidenschaft für das Schreiben

Why does the sentence use über (über ihre Leidenschaft) and not von (von ihrer Leidenschaft)?

Both über and von can sometimes be translated as about, but there is a nuance:

über + accusative: talking about a topic, often in a more “thematic” or detailed way
- über ihre Leidenschaft = about her passion (as a subject of discussion)
von + dative: more like of / from, often used for source, origin, or looser associations

In the context of speaking about a topic, über is more standard and neutral:

Sie spricht über ihre Leidenschaft. = She talks about her passion.
Sie spricht von ihrer Leidenschaft. = Also possible, but can sound a bit more like “she mentions” or “she speaks of” it, often slightly less focused on it as a central topic.

Here, über fits very well because her passion for writing is clearly the main topic of what she talks about.

What case is ihre Leidenschaft in, and why is it ihre and not ihrer?

Über in this context takes the accusative case.

Leidenschaft is feminine (die Leidenschaft).
Feminine accusative with a possessive pronoun (ihr-) uses the form ihre.

Cases for die Leidenschaft (singular):

Nominative: die Leidenschaft / ihre Leidenschaft
Accusative: die Leidenschaft / ihre Leidenschaft
Dative: der Leidenschaft / ihrer Leidenschaft
Genitive: der Leidenschaft / ihrer Leidenschaft

Because über here uses the accusative, we get:

über ihre Leidenschaft, not über ihrer Leidenschaft.

Why is it für das Schreiben and not just für Schreiben or something like zum Schreiben?

Für das Schreiben uses das Schreiben as a noun (a nominalized verb):

schreiben (lowercase) = to write (verb)
das Schreiben (capitalized) = the act of writing / writing (as a thing, an activity)

With Leidenschaft für …, German very often uses a noun:

Leidenschaft für Musik
Leidenschaft für Sport
Leidenschaft für das Schreiben

Other options are possible but slightly different:

für Schreiben (without article)
– sounds incomplete or unidiomatic here; you usually add das when you treat it as a concrete activity.
Leidenschaft fürs Schreiben
– fürs = für das, this is just the contracted form and is very common in speech and writing.
Leidenschaft, zu schreiben
– also possible, but focuses more on the activity of writing from the subject’s perspective (“her passion to write”) rather than “her passion for writing” as a thing.

In this sentence, für das Schreiben is the most neutral, textbook-like way to express for writing.

Why is Schreiben capitalized, while spricht is not?

In German, verbs used as nouns (nominalized verbs) are capitalized.

sprechen → spricht: remains a verb, so it stays lowercase.
schreiben as a verb: lowercase.
das Schreiben (the act of writing): the verb is turned into a noun, so it is capitalized.

Rule of thumb:
If an infinitive is used with an article (das, ein, etc.) or clearly as a thing, it becomes a noun and is capitalized:

Das Lesen macht Spaß. (Reading is fun.)
Beim Kochen höre ich Musik. (While cooking, I listen to music.) – Kochen is also nominalized here.

Can I also say Leidenschaft fürs Schreiben instead of Leidenschaft für das Schreiben?

Yes, absolutely.

fürs is the contracted form of für das:
- für das Schreiben → fürs Schreiben

Both are grammatically correct and mean the same thing:

ihre Leidenschaft für das Schreiben
ihre Leidenschaft fürs Schreiben

Fürs Schreiben sounds a bit more colloquial and is very common in everyday language. In careful or formal writing, many people still prefer für das Schreiben, but both are accepted.

Could I replace spricht with redet or erzählt? What is the difference?

You could, but the nuance changes slightly:

sprechen (sie spricht)
Neutral “to speak / talk”. Often slightly more neutral or formal.
Sie spricht über ihre Leidenschaft für das Schreiben.
reden (sie redet)
More colloquial “to talk / chat”. Often used in everyday speech.
Sie redet mit leuchtenden Augen über ihre Leidenschaft … is fine and sounds a bit more casual.
erzählen (sie erzählt)
Means “to tell, to narrate”. It usually implies telling a story or giving more detailed information.
Sie erzählt mit leuchtenden Augen von ihrer Leidenschaft für das Schreiben.
Here you would more naturally use von instead of über, because she is telling about her experiences with it.

So:

sprechen über → talk about (neutral)
reden über → talk about (more colloquial)
erzählen von → tell (stories) about.

Can I change the word order and say Meine Schwester spricht über ihre Leidenschaft für das Schreiben mit leuchtenden Augen?

Yes, that sentence is still grammatically correct.

Both orders are possible:

Meine Schwester spricht mit leuchtenden Augen über ihre Leidenschaft für das Schreiben.
– Emphasis a bit more on how she speaks (with shining eyes).
Meine Schwester spricht über ihre Leidenschaft für das Schreiben mit leuchtenden Augen.
– Emphasis a bit more on what she talks about, with the manner added afterwards.

In German, adverbial phrases (like mit leuchtenden Augen) are quite flexible. The original version is slightly more natural because it groups the manner more closely with the verb spricht: spricht mit leuchtenden Augen …

Why is it meine Schwester and not mein Schwester?

Because Schwester is a feminine noun:

die Schwester = the sister
mein / meine change according to gender and case.

In the nominative singular:

Masculine: mein Bruder (my brother)
Feminine: meine Schwester (my sister)
Neuter: mein Kind (my child)
Plural: meine Geschwister (my siblings)

Here, Meine Schwester is the subject in the nominative case, and Schwester is feminine, so you need meine.

Why is Augen plural here, and how does that affect the grammar?

Augen is the plural of das Auge (eye).

You normally speak of eyes (plural) when describing someone’s expression:

mit leuchtenden Augen = with shining eyes

Because it is plural, the dative plural form is used after mit, and the adjective takes the -en ending:

Singular dative: mit leuchtendem Auge (with a shining eye – unusual meaning)
Plural dative: mit leuchtenden Augen (with shining eyes – natural meaning)

So the plural Augen triggers both:

the plural noun ending -en
the adjective ending -en in the dative plural.

Why is it leuchtenden and not something like an adverb form leuchtend?

In mit leuchtenden Augen, leuchtenden is an adjective that directly describes the noun Augen.

Adjective before a noun → it is an attributive adjective.
Attributive adjectives in German must take an ending that reflects case, gender, and number.

Here:

Preposition mit → dative
Noun Augen → plural
Adjective before the noun → needs dative plural ending -en

So:

leuchtend (base form, no grammar info)
leuchtenden Augen (dative plural, required after mit)

An adverb would modify the verb directly, for example:

Sie spricht leuchtend. (This sounds odd in German and doesn’t mean “with shining eyes”.)

To express “with shining eyes,” German naturally uses an adjective + noun in a prepositional phrase: mit leuchtenden Augen.