Learn Hardcore German: Im Empfehlungsschreiben beschreibt die Professorin, wie zuverlässig ich bin. - In the letter of recommendation the professor describes how reliable I am.

You could say the full form In dem Empfehlungsschreiben, and it would still be correct, but in normal speech and writing, Germans almost always use the contraction im here.

What case is Empfehlungsschreiben in, and why?

Empfehlungsschreiben is in the dative case in this sentence, because of the preposition in.

In German, in can take:

accusative (movement into something):
- Ich gehe in das Büro. – I go into the office.
dative (location in/inside something):
- Ich bin in dem Büro. – I am in the office.

In the sentence Im Empfehlungsschreiben beschreibt die Professorin …, we are talking about location (in the letter), not movement, so in + dative is used → in dem Empfehlungsschreiben → im Empfehlungsschreiben.

Why is Empfehlungsschreiben written as one long word and capitalized?

German loves compound nouns: several words combined into one noun.

Here:

die Empfehlung = recommendation
das Schreiben = letter / written document
das Empfehlungsschreiben = letter of recommendation

Rules relevant here:

Compound nouns are usually written as one word.
All nouns in German are capitalized, so Empfehlungsschreiben starts with a capital E.

That’s why you see Empfehlungsschreiben as one capitalized word.

Is Empfehlungsschreiben masculine, feminine, or neuter? How can I tell?

Empfehlungsschreiben is neuter: das Empfehlungsschreiben.

You can’t see this directly in the sentence because the article is hidden in the contraction im (= in dem). Dem is used for both masculine and neuter in the dative singular, so it doesn’t distinguish them.

To know its gender, you have to learn the noun:

dictionary form: das Empfehlungsschreiben (neuter)

A small pattern that sometimes helps: many nouns ending in -schreiben (from schreiben, “to write”) are neuter. But in general, you need to learn the gender with the noun.

Why is it die Professorin and not der Professor?

German marks grammatical gender on many profession titles:

der Professor = male professor
die Professorin = female professor

The ending -in is the usual feminine ending for professions (singular), and the article switches to die for feminine singular.

So die Professorin tells you the professor is female. If you wanted a male professor, you’d write der Professor instead.

Why is the verb beschreibt in second position after Im Empfehlungsschreiben instead of right after die Professorin?

German main clauses follow the V2 rule: the conjugated verb must be in second position.

“Second position” means second element, not second word.

The sentence elements are:

Im Empfehlungsschreiben (prepositional phrase) – element 1
beschreibt (verb) – element 2
die Professorin (subject) – element 3
wie zuverlässig ich bin (subordinate clause)

So the word order satisfies the rule: > [Element 1] Im Empfehlungsschreiben
> [Element 2] beschreibt
> [Element 3] die Professorin …

You could also say:

Die Professorin beschreibt im Empfehlungsschreiben, wie zuverlässig ich bin.

Here:

Die Professorin – element 1
beschreibt – element 2

Both orders are correct; they just put different emphasis on what comes first.

What is the difference between Im Empfehlungsschreiben beschreibt die Professorin … and Die Professorin beschreibt im Empfehlungsschreiben …?

Both sentences are grammatically correct and mean the same thing in most contexts. The difference is emphasis:

Im Empfehlungsschreiben beschreibt die Professorin …
→ Starts with the letter; it slightly emphasizes where the description appears.
Die Professorin beschreibt im Empfehlungsschreiben …
→ Starts with the professor; it slightly emphasizes who is doing the describing.

In everyday conversation, both would be understood the same way; it’s mostly a stylistic choice.

Why is there a comma before wie zuverlässig ich bin?

The part wie zuverlässig ich bin is a subordinate clause (Nebensatz). In German, subordinate clauses are normally separated from the main clause by a comma.

Structure:

Main clause: Im Empfehlungsschreiben beschreibt die Professorin
Subordinate clause: wie zuverlässig ich bin

The comma marks the boundary: > Im Empfehlungsschreiben beschreibt die Professorin, wie zuverlässig ich bin.

German comma rules are stricter than English: subordinate clauses almost always must be preceded by a comma.

Why is the verb bin at the very end of wie zuverlässig ich bin?

In German subordinate clauses, the conjugated verb goes to the end of the clause.

Compare:

Main clause: Ich bin zuverlässig. (verb in 2nd position)
Subordinate clause: … wie zuverlässig ich bin. (verb at the end)

In wie zuverlässig ich bin:

wie = subordinator (“how”)
zuverlässig = adjective (“reliable”)
ich = subject
bin = conjugated verb → goes to the end in a subordinate clause

So the word order wie zuverlässig ich bin is required by German grammar.

Why is it wie zuverlässig ich bin and not dass ich zuverlässig bin?

Both wie and dass can introduce subordinate clauses, but they have different meanings:

wie = how / in what way / how (much)
- Sie beschreibt, wie zuverlässig ich bin.
  → She describes how reliable I am / to what extent I am reliable.
dass = that
- Sie beschreibt, dass ich zuverlässig bin.
  → She describes that I am reliable (she states the fact).

In your sentence, wie focuses on the degree or manner of reliability, which fits better with “describes”.
Dass ich zuverlässig bin is grammatically correct, but sounds more like she is simply reporting the fact, not describing the way in which you are reliable.

Is zuverlässig an adjective or an adverb here, and why doesn’t it change its form?

zuverlässig is an adjective here, used as a predicate adjective after the verb sein (to be):

ich bin zuverlässig = I am reliable.

Predicate adjectives in German:

are not declined (no extra endings)
keep their basic form after sein, werden, bleiben, etc.

You only see endings when the adjective is in front of a noun:

ein zuverlässiger Mitarbeiter – a reliable employee
zuverlässige Mitarbeiter – reliable employees

But after bin, it stays just zuverlässig.

Why is the tense beschreibt (present) used, even if the letter was written in the past?

German, like English, often uses the “literary” present tense to talk about the contents of texts, films, letters, etc.

Even if the letter was written earlier, we can say:

In seinem Buch schreibt er … – In his book he writes …
Im Empfehlungsschreiben beschreibt die Professorin … – In the letter of recommendation the professor describes …

The idea is: the letter still exists now and its contents are valid now, so present tense is natural. You could use a past tense with context, but the present is standard when summarizing written content.

Can I also say In dem Empfehlungsschreiben instead of Im Empfehlungsschreiben, or is that wrong?

You can say In dem Empfehlungsschreiben, and it is grammatically correct.

However:

In normal spoken and written German, the contracted form im is much more natural here.
The full form in dem might sound slightly more formal or emphatic, or appear in contexts where you need to stress dem (“that particular letter”).

For everyday use, Im Empfehlungsschreiben is the default choice.