An der Sicherheitskontrolle zeige ich die Bordkarte.

German prepositions do not match English prepositions one-to-one. An can mean on, at, or by, depending on the context.

In An der Sicherheitskontrolle, the natural English translation is at the security checkpoint / at security. So even though an often gets taught as on, here it is best understood as at.

Because am is a contraction of an dem.

That only works with dem, which is the dative article for masculine and neuter nouns. But Sicherheitskontrolle is feminine: die Sicherheitskontrolle.

So in the dative, it becomes der:

• die Sicherheitskontrolle → nominative
• an der Sicherheitskontrolle → dative after an

So am Sicherheitskontrolle is not possible here.

An is a two-way preposition in German. That means it can take either:

• accusative for movement toward a destination
• dative for location

Here the sentence describes a location: at the security checkpoint. There is no movement toward it in this sentence, so German uses the dative:

• an der Sicherheitskontrolle = at the security checkpoint

If it were about movement toward something, you would expect accusative instead.

This is because German follows the verb-second rule in main clauses.

The first position in the sentence is taken by An der Sicherheitskontrolle. Once that happens, the conjugated verb must still come second, so zeige comes next, and the subject ich follows it:

• An der Sicherheitskontrolle | zeige | ich | die Bordkarte

So this word order is completely normal. German is not making a question here; it is just putting the location first.

Yes. That is also grammatical.

Compare:

• An der Sicherheitskontrolle zeige ich die Bordkarte.
• Ich zeige die Bordkarte an der Sicherheitskontrolle.

Both mean the same basic thing. The version with An der Sicherheitskontrolle first puts more attention on the location, almost like At security, I show the boarding pass.

Zeige is the 1st person singular present tense of zeigen:

• ich zeige = I show
• du zeigst = you show
• er/sie/es zeigt = he/she/it shows

So zeige ich still means I show. The subject is ich; the verb is just placed before it because of normal German word order.

It is the accusative object, because it is the thing being shown.

With zeigen, the thing you show is usually in the accusative:

• Ich zeige die Bordkarte.

A helpful detail: for feminine singular nouns, the article die is the same in both nominative and accusative. So even though the form does not change, the function does:

• die Bordkarte can be nominative
• die Bordkarte can also be accusative

Here it is accusative because it is the direct object.

German often uses the definite article where English might use a possessive like my, especially when the ownership is obvious from the situation.

At airport security, it is naturally understood that you are showing your boarding pass, so die Bordkarte sounds perfectly normal.

You could also say meine Bordkarte, but that would add a little more emphasis to the fact that it is yours.

Both are used.

• Bordkarte is a standard German word.
• Boardingpass is also very common in everyday speech.

So a learner should recognize both. In a sentence like this, Bordkarte is perfectly natural and slightly more formally German.

German often combines nouns into one compound word.

Sicherheitskontrolle is made from:

• Sicherheit = security, safety
• Kontrolle = check, inspection, control

Together they mean security check / security screening.

The gender of a German compound is usually determined by the last part. Since Kontrolle is feminine (die Kontrolle), the whole compound is also feminine:

• die Sicherheitskontrolle

Because they are nouns.

In German, all nouns are capitalized, not just proper names. So:

• die Sicherheitskontrolle
• die Bordkarte

This is one of the most noticeable differences from English spelling.