Learn Hardcore German: Durch regelmäßige Wiederholung bleiben die neuen Wörter länger im Kopf. - Through regular repetition the new words stay in my head longer.

In this sentence, Durch regelmäßige Wiederholung means “through regular repetition / by repeating regularly”. It describes the means or method by which the words stay in your head.

Grammatically:

durch always takes the accusative case.
Wiederholung is a feminine noun (die Wiederholung). In the accusative singular feminine, the ending is the same as nominative: die Wiederholung.
There’s no article here (no die), so we have a “zero article” (general statement).
With no article, the adjective takes a strong ending: regelmäßige.

So:

Preposition: durch (+ accusative)
Case: accusative singular feminine
Form: (durch) regelmäßige Wiederholung

Why is the verb bleiben in second position, even though the sentence doesn’t start with the subject?

German main clauses follow the V2 rule (verb in second position):

The conjugated verb must be the second element in the sentence.
“Element” means a whole chunk (phrase), not a single word.

In this sentence:

Durch regelmäßige Wiederholung = first element (a prepositional phrase)
bleiben = second element (finite verb)
die neuen Wörter = subject (third element)
länger im Kopf = rest of the predicate

So, even though the subject die neuen Wörter is not at the beginning, the verb bleiben is still in second position, which is correct German word order:

Durch regelmäßige Wiederholung bleiben die neuen Wörter länger im Kopf.
Compare with a subject-first version: Die neuen Wörter bleiben durch regelmäßige Wiederholung länger im Kopf. (same verb position: second)

Why is it bleiben and not something like sind or werden?

Bleiben means to stay / to remain. Here it expresses continuation over time:

bleiben … im Kopf = remain in your head, stay in your memory

If you said:

… sind länger im Kopf, that sounds more like a simple state: “are in the head (for longer)” – grammatically OK, but less idiomatic in this context.
… werden länger im Kopf, would suggest “become longer in the head”, which doesn’t fit the idea.

Using bleiben emphasizes that the words stay there for a longer time, which is exactly what is meant.

What case is die neuen Wörter, and why is it neuen, not neue?

Die neuen Wörter is the subject of the sentence, so it’s in the nominative plural.

Plural definite article in nominative: die
Noun: Wörter (plural of das Wort)

With a definite article (die) in the plural, adjectives usually take the ending -en (weak declension):

nominative plural with die → die neuen Wörter

So:

Case: nominative plural
Article: die
Adjective ending: -en → neuen

That’s why it’s die neuen Wörter, not die neue Wörter.

Why is it Wörter and not Worte?

German has two plural forms of das Wort:

Wörter – used for individual, countable words as vocabulary items.
- e.g. Ich kenne diese drei Wörter. – “I know these three words.”
Worte – used for connected words in a saying, a speech, a quotation, or a “set of words” as a whole.
- e.g. Seine letzten Worte waren … – “His last words were …”

In this sentence, we’re clearly talking about individual vocabulary items you want to remember, so Wörter is the correct plural:

die neuen Wörter = “the new vocabulary items / the new words”

Why is it im Kopf and not in dem Kopf?

Im is just the contraction of in dem:

in (preposition) + dem (dative masculine/neuter) → im

So im Kopf literally equals in dem Kopf.

This contraction is very common in spoken and written German, especially in fixed expressions:

im Haus (in dem Haus) – in the house
im Sommer (in dem Sommer) – in the summer
im Kopf (in dem Kopf) – in the head / in one’s mind

Here, Kopf is masculine (der Kopf). With the preposition in meaning location (where something is), German uses the dative:

masculine dative singular of der Kopf = dem Kopf → contracted to im Kopf

Why is Kopf in the dative case here?

The preposition in can take either dative or accusative, depending on meaning:

dative = location (where something is)
accusative = direction/motion (where something is going)

In this sentence, the words are located in your head (they stay there):

It’s about where they remain → location → dative.

So:

Preposition: in (here: location) → dative
Noun: der Kopf (masculine)
Dative singular masculine: dem Kopf → contracted to im Kopf

Is Wiederholung singular or plural here, and why is there no article?

Wiederholung is singular in this sentence:

regelmäßige Wiederholung = “regular repetition” (an abstract, uncounted concept)

There is no article because we’re talking about repetition in general as a habit or method, not about one specific repetition:

Durch regelmäßige Wiederholung = “Through (the process of) repeating regularly”

If you said:

Durch die regelmäßige Wiederholung – this would sound more like you’re referring to some particular repetition that was mentioned before.

German often omits the article with abstract, uncountable, or general concepts:
durch Übung, mit Geduld, bei Arbeit (in some expressions), etc.

Why is it regelmäßige Wiederholung, but neuen Wörter? The adjective endings are different: -e vs -en.

The adjective ending depends on two main things:

Case, gender, number of the noun
Whether there is a determiner (like a definite article) before it

In this sentence:

regelmäßige Wiederholung
- Preposition durch → accusative
- Wiederholung is feminine singular
- There is no article (die is omitted)
- With no article, adjectives take strong endings → regelmäßige
die neuen Wörter
- Subject → nominative plural
- There is a definite article: die
- With die (or der, das, etc.) in plural, adjectives take weak endings → neuen

So:

regelmäßige Wiederholung = accusative singular feminine, no article → -e
die neuen Wörter = nominative plural with die → -en

Could you move durch regelmäßige Wiederholung to a different place in the sentence, and would the meaning change?

Yes, you can move that phrase without changing the basic meaning. Possible variants:

Die neuen Wörter bleiben durch regelmäßige Wiederholung länger im Kopf.
Die neuen Wörter bleiben länger durch regelmäßige Wiederholung im Kopf. (less natural, but understandable)

What changes is mainly:

Emphasis and style, not the core meaning.

Putting Durch regelmäßige Wiederholung first:

Durch regelmäßige Wiederholung bleiben die neuen Wörter länger im Kopf.

highlights the method (“through regular repetition”) as the most important information. That’s a common stylistic choice in German when you want to emphasize cause, time, or manner.