Learn Hardcore German: Ich überprüfe das Dokument sorgfältig.

It’s the direct object of überprüfen (“to check”), so it takes the accusative case. For neuter nouns, the definite article is das in both nominative and accusative, so it remains das.

Why doesn’t überprüfen split into über and prüfen here?

Überprüfen is a verb with an inseparable prefix (über-). Verbs with inseparable prefixes (be-, emp-, ent-, er-, ge-, miss-, ver-, zer-) never split in main‐clause word order and never take ge- in the past participle.

How do I form the past participle and the perfect tense of überprüfen?

Because it has an inseparable prefix, the past participle is formed without ge-:
• Past participle: überprüft
• Perfect tense: Ich habe das Dokument überprüft.

Why is sorgfältig not declined like an adjective?

Here sorgfältig is an adverb modifying the verb überprüfe (“I check”). Adverbs in German are never declined. Only adjectives directly before a noun (attributive adjectives) get case endings.

Can I change the word order and still keep the meaning?

Yes. German gives you flexibility to emphasize different parts:
• Sorgfältig überprüfe ich das Dokument. (emphasizes how you check)
• Das Dokument überprüfe ich sorgfältig. (emphasizes what you check)

What’s the difference between prüfen and überprüfen?

• prüfen = to examine, test, or inspect in a general sense
• überprüfen = to verify, check accuracy or correctness; implies a more thorough or confirmatory check

How does kontrollieren compare to überprüfen?

Both can mean “to check,” but:
• kontrollieren often implies inspecting or controlling (e.g. tickets, borders)
• überprüfen is used for verifying details, facts, correctness

What other adverbs could I use instead of sorgfältig?

You can choose based on nuance:
• gründlich (thoroughly)
• genau (exactly/precisely)
• aufmerksam (attentively)
You can also add degree modifiers: sehr sorgfältig, äußerst gründlich.