Learn Hardcore German: Der Maler reinigt seinen Pinsel nach der Arbeit. - The painter cleans his brush after the work.

seinen Pinsel is in the accusative case because Pinsel is the direct object of the verb reinigt. Since Pinsel is masculine (der Pinsel), the masculine accusative ending -en is added to the possessive pronoun sein, forming seinen.

Why is the possessive pronoun seinen used instead of just sein?

Possessive pronouns in German must agree in gender, number and case with the noun they modify. Here, Pinsel is masculine singular and is the direct object (accusative case), so sein takes the masculine accusative ending -en, giving seinen.

What role does der Maler play in this sentence and what case is it in?

der Maler is the subject of the sentence, the one performing the action (cleaning). As the subject, it stands in the nominative case. Maler is masculine singular, so its nominative article is der.

Why is the verb reinigt placed where it is, and what form is it?

In a main clause German follows the verb‑second (V2) rule: the finite verb must occupy the second position. Here, Der Maler is first, reinigt (3rd person singular present of reinigen) is second, followed by the object and the time expression.

Why is there no definite article before Pinsel?

Because the possessive pronoun seinen already functions as a determiner. You don’t use a separate article when you have a possessive pronoun in front of a noun.

What case does the phrase nach der Arbeit use and why?

The preposition nach always requires the dative case. Arbeit is feminine (die Arbeit); its dative singular form is der Arbeit, giving nach der Arbeit.

Can I move nach der Arbeit to the beginning of the sentence? How does the word order change?

Yes. If you start with Nach der Arbeit, the conjugated verb remains in second position, and the subject follows it:
Nach der Arbeit reinigt der Maler seinen Pinsel.

How would the sentence change if the painter cleaned multiple brushes?

Use the plural forms. Pinsel stays the same in plural, and the plural accusative possessive pronoun is seine:
Der Maler reinigt seine Pinsel nach der Arbeit.

How do I know the genders of Maler, Pinsel and Arbeit?

There are patterns (with exceptions), but the safest way is to learn each noun with its article. Common endings include:
• -er and -el often indicate masculine (der Maler, der Pinsel)
• -eit, -schaft, -ung often indicate feminine (die Arbeit)
Always memorize the article (der, die, das) along with the noun.