Das Formular fragt nach dem Geschlecht.

Because Formular is a neuter noun in German, and the nominative singular definite article for neuter nouns is das.

• der = masculine
• die = feminine
• das = neuter

So:

• das Formular = the form

In this sentence, das Formular is also the subject, so it stays in the nominative case.

Because nachfragen nach or fragen nach is a common German pattern meaning to ask for / to ask about something.

So:

• jemanden fragen = to ask someone
• nach etwas fragen = to ask for/about something

Examples:

• Ich frage den Lehrer. = I ask the teacher.
• Ich frage nach dem Termin. = I ask about the appointment.

In your sentence:

• Das Formular fragt nach dem Geschlecht.
• literally: The form asks about/for the gender.

So nach is important here because it shows what information is being requested.

Because the preposition nach takes the dative case in this meaning.

The noun is das Geschlecht in the dictionary form, but after nach, it changes to dative:

• nominative: das Geschlecht
• dative: dem Geschlecht

So:

• nach dem Geschlecht

This is one of the main things learners need to remember: the article often changes because of the case required by the preposition.

Yes, nach is a dative preposition.

That means the noun phrase after it will be in the dative:

• nach dem Namen
• nach der Adresse
• nach den Kosten

So in this sentence:

• nach dem Geschlecht is correct because Geschlecht is neuter singular, and the dative article is dem.

fragt is the 3rd person singular form of the verb fragen in the present tense.

Conjugation of fragen:

• ich frage
• du fragst
• er/sie/es fragt
• wir fragen
• ihr fragt
• sie/Sie fragen

Since the subject is das Formular = it, the verb form is:

• Das Formular fragt

Grammatically, yes. German often uses this kind of wording, just like English can say:

• The form asks for your address.
• The questionnaire asks about your age.

So although a form is not literally speaking, it is treated as the subject of the sentence. This is completely natural in German.

Normally, no. That sounds unnatural in German.

If you say jemanden/etwas fragen, the direct object is usually a person or occasionally a question, not the kind of information being requested in this context.

Natural options include:

• Das Formular fragt nach dem Geschlecht.
• Im Formular wird nach dem Geschlecht gefragt.
• Das Formular verlangt die Angabe des Geschlechts. (more formal)

So for forms and requested information, nach + dative is the usual and natural structure here.

In this context, Geschlecht usually means gender or sex, depending on the form and context.

German Geschlecht can be used in different ways:

• biological sex
• gender on a form
• in other contexts, even lineage/family line or grammatical gender

In the sentence Das Formular fragt nach dem Geschlecht, it usually refers to the category the form wants you to specify, such as male, female, diverse, etc.

Yes, German word order is flexible, but the verb still stays in second position in a main clause.

Standard order:

• Das Formular fragt nach dem Geschlecht.

A different emphasis:

• Nach dem Geschlecht fragt das Formular.

That second version is grammatically correct, but it is less neutral and sounds more marked or literary. The first version is the normal one learners should use.

Because Geschlecht is a singular neuter noun, and many singular nouns in German do not change their noun ending in the dative.

What changes here is mainly the article:

• das Geschlecht → dem Geschlecht

So the noun itself stays the same.

Compare that with some plural datives, where the noun often does add -n:

• die Kinder → mit den Kindern

But in your sentence, singular neuter:

• dem Geschlecht

Yes. German forms and official language often use more formal wording, for example:

• Im Formular wird nach dem Geschlecht gefragt.
• Bitte geben Sie Ihr Geschlecht an.
• Angabe des Geschlechts
• Das Formular verlangt die Angabe des Geschlechts.

Your original sentence is perfectly correct and natural, but official German often prefers more impersonal or formal phrasing.