Learn Hardcore German: Die Kollegin entwickelt eine App für unsere Bibliothek. - The female colleague is developing an app for our library.

Die Kollegin = the (female) colleague
Just Kollegin entwickelt … would sound incomplete in normal prose, a bit like saying “Colleague is developing an app …” in English.

You could drop the article only in special contexts (headlines, notes, labels), e.g. on an office door: Kollegin im Gespräch (“Colleague in a meeting”). In normal sentences, you keep the article.

Why Kollegin and not Kollege?

German job titles and many role nouns have masculine and feminine forms:

der Kollege = male colleague
die Kollegin = female colleague

So die Kollegin tells you the colleague is female.
If you don’t want to specify gender, you might see forms like die Kollegin oder der Kollege, die Kolleg*innen, etc., but here the sentence clearly refers to a female person.

Why is the article die with Kollegin, but eine with App?

Two different things are going on:

Definite vs. indefinite
- die Kollegin = the colleague (a specific one everyone knows in the context)
- eine App = an app (not specified which app)
Gender and case:
- Kollegin is feminine; nominative singular feminine definite article is die.
- App is also treated as feminine; accusative singular feminine indefinite article is eine.

So: die Kollegin (subject, specific person) and eine App (direct object, non‑specific thing).

Why is the verb entwickelt and not entwickeln?

Entwickeln is the infinitive (“to develop”).
In the sentence, the subject is die Kollegin (3rd person singular), so the verb must be conjugated:

ich entwickle
du entwickelst
er/sie/es entwickelt
wir entwickeln
ihr entwickelt
sie entwickeln

Since die Kollegin = sie (she), you use entwickelt.

So Die Kollegin entwickelt … = “The colleague develops / is developing …”

What tense is entwickelt? How do I express English “is developing”?

Entwickelt here is present tense (Präsens).

German usually uses the simple present for both:

“The colleague develops an app …”
“The colleague is developing an app …”

Both are normally just: Die Kollegin entwickelt eine App …

You don’t need a special continuous/progressive form. Forms like ist am Entwickeln exist but are more colloquial and not needed here.

Why eine App and not ein App?

The choice ein / eine depends on the grammatical gender of the noun:

die App is treated as feminine in German.
Feminine accusative singular with the indefinite article is eine.

Therefore: eine App, not ein App.

(For comparison: ein Programm – “a program” – because Programm is neuter: das Programm.)

Is App really a German word? What gender and plural does it have?

App is a loanword from English but it’s fully integrated into German:

Gender: feminine – die App
Plural: die Apps

Examples:

Ich habe drei neue Apps heruntergeladen. – “I downloaded three new apps.”
Die App funktioniert nicht. – “The app doesn’t work.”

Why für unsere Bibliothek and not something like für unserer Bibliothek?

Two key points:

Preposition “für”
- für always takes the accusative case in German.
Case of “unsere Bibliothek”
- Bibliothek is feminine: die Bibliothek.
- Feminine accusative singular of unsere is unsere (same form as nominative).
- unsere Bibliothek is therefore accusative, not nominative/dative.

Unserer Bibliothek would be dative and would be wrong after für.
So the correct form is für unsere Bibliothek.

Why is Bibliothek capitalized?

In German, all nouns are capitalized, regardless of their position in the sentence.

So:

die Bibliothek – “the library”
eine App – “an app”
Die Kollegin – “the colleague”

This is a rule: if it’s a noun, you capitalize it. Adjectives, verbs, etc. are normally not capitalized (except at the start of a sentence or in special cases).

What is the word order here? Could I say Die Kollegin entwickelt für unsere Bibliothek eine App?

The sentence uses standard main-clause word order: Subject – Verb – Objects/Adverbials

Subject: Die Kollegin
Verb: entwickelt
Direct object: eine App
Prepositional phrase: für unsere Bibliothek

So: Die Kollegin entwickelt eine App für unsere Bibliothek.

Yes, you can say:

Die Kollegin entwickelt für unsere Bibliothek eine App.

Both are grammatically correct. The second version slightly emphasizes für unsere Bibliothek, as the information that comes right after the verb is often more prominent. But in everyday speech, both versions sound natural.

Why isn’t there something like am Entwickeln or ist am Entwickeln, like English “is developing”?

German doesn’t need a special progressive form to express an ongoing action. The simple present is usually enough:

Die Kollegin entwickelt eine App …
= “The colleague develops / is developing an app …”

Expressions like:

Die Kollegin ist am Entwickeln.
Die Kollegin ist dabei, eine App zu entwickeln.

also exist and can emphasize that the process is ongoing, but in most contexts, they’re not necessary and can sound more colloquial or stylistically marked. The neutral, standard version is just the simple present.

What’s the difference between unsere Bibliothek and der Bibliothek or eine Bibliothek?

These words express different ideas:

unsere Bibliothek = our library (possessive, some group “we” owns or is associated with it)
die Bibliothek = the library (specific one already known in the context)
eine Bibliothek = a library (not specified which one)

In the sentence, unsere Bibliothek makes it clear that the app is for the library that belongs to or is used by the speaker’s group (e.g. “our company library” or “our university library”). If you said für die Bibliothek, it could be any known library; für eine Bibliothek would be for some library, not specified whose.

Does Kollegin always mean “co-worker,” or can it also mean “classmate,” like English “colleague”?

Kollegin / Kollege in German usually means:

a colleague at work (same company / organization)
sometimes also a colleague in the same profession (e.g. two doctors talking about each other)

It is not used for classmates at school or university. For those, you’d usually say:

Mitschülerin / Mitschüler (school)
Kommilitonin / Kommilitone (university, more formal/academic)

So here, die Kollegin is a co-worker or professional colleague, not a classmate.