De grammatica-oefening helpt ons om de nieuwe woorden beter te begrijpen.

Because the subject is De grammatica-oefening, which is singular: the grammar exercise.

In the present tense, Dutch verbs change according to the subject:

• ik help
• jij helpt
• hij/zij/het helpt
• de oefening helpt
• wij helpen

So helpt is the correct third-person singular form of helpen.

Ons is the object pronoun, while wij is the subject pronoun.

Here, the exercise is doing the helping, so de grammatica-oefening is the subject. Us is receiving the action, so Dutch uses ons:

• wij = we
• ons = us

Compare:

• Wij begrijpen de woorden. = We understand the words.
• De oefening helpt ons. = The exercise helps us.

This is a very common Dutch structure: om + te + infinitive.

It introduces an infinitive phrase, often similar to English to understand or in order to understand.

So:

• helpt ons om ... te begrijpen = helps us to understand ...
• literally: helps us in order to understand ...

After helpen, Dutch often uses either:

• helpen + object + om + te + infinitive
• or helpen + object + te + infinitive

So you may also hear:

• De grammatica-oefening helpt ons de nieuwe woorden beter te begrijpen.

Both are normal. The version with om can sound a bit clearer or a bit more formal.

Because in Dutch, an infinitive with te usually goes to the end of the clause.

In the phrase:

• om de nieuwe woorden beter te begrijpen

the main infinitive is begrijpen, so it comes last.

This is very typical Dutch word order. English often keeps the verb earlier, but Dutch likes to place the infinitive at the end in these constructions.

You can think of the structure like this:

• om
  • other information + te begrijpen

Examples:

• Ik probeer Nederlands te leren.
• Zij komt hier om te werken.
• Dit helpt ons de regels beter te begrijpen.

Because the adjective nieuw gets an extra -e here: nieuwe.

Dutch adjectives usually take -e when they come before:

• a de-word
• a plural noun
• or most nouns with a definite article

Since woorden is plural, the adjective must be nieuwe.

So:

• het nieuwe woord = the new word
• de nieuwe woorden = the new words

This -e ending is extremely common in Dutch adjective agreement.

Because woorden is plural, and in Dutch all plural nouns take the article de.

So even if the singular noun is a het-word, the plural still uses de.

For example:

• het woord = the word
• de woorden = the words

That is why the sentence has de nieuwe woorden.

The main noun here is oefening (exercise), and oefening is a de-word.

In Dutch compounds, the article is determined by the last/main part of the compound noun. So:

• oefening is a de-word
• therefore grammatica-oefening is also a de-word

A useful pattern is that many nouns ending in -ing are de-woorden.

So:

• de oefening
• de grammatica-oefening

Dutch very often forms compound nouns, where English might use separate words.

So grammatica-oefening is a compound meaning something like:

• grammar exercise

Dutch prefers to build one noun out of two parts:

• grammatica = grammar
• oefening = exercise

Together they function as a single noun.

This is very common in Dutch, for example:

• taalboek = language book
• huiswerkopdracht = homework assignment
• woordenschatlijst = vocabulary list

Beter means better, and here it modifies begrijpen.

So:

• de woorden begrijpen = understand the words
• de woorden beter begrijpen = understand the words better

This is a common Dutch way to express improvement in how well someone does something.

A useful point for English speakers: Dutch often uses forms of goed / beter / best in places where English uses well / better / best.

So although English says understand better, Dutch says:

• beter begrijpen

Yes. A very natural alternative is:

• De grammatica-oefening helpt ons de nieuwe woorden beter te begrijpen.

After helpen, both patterns are common:

• helpen iemand om iets te doen
• helpen iemand iets te doen

The version with om is not wrong at all; it just makes the infinitive structure more explicit.

So both are good Dutch.

Yes, very often.

In Dutch, te + infinitive is often the equivalent of English to + verb:

• te begrijpen = to understand
• te leren = to learn
• te lezen = to read

In this sentence, the larger phrase is:

• om de nieuwe woorden beter te begrijpen

which corresponds to:

• to understand the new words better
• or in order to understand the new words better

So if you see te + infinitive, it is often a good first guess to think of English to + verb.