Die Passform ist an der Taille zu eng.

Because Passform is a feminine noun in German, so its nominative singular article is die.

• die Passform = the fit
• die Form is also feminine, which may help you remember it

In this sentence, die Passform is the subject, so it stays in the nominative case.

Passform means fit, especially the way a piece of clothing fits on the body.

It is commonly used for:

• clothes
• shoes
• uniforms
• tailored items

So Die Passform ist ... zu eng means the clothing’s fit is too tight in a certain area.

German main clauses normally follow the verb-second rule.

Here the structure is:

• Die Passform = position 1
• ist = position 2
• an der Taille = additional information
• zu eng = complement

So the sentence order is completely normal for a German statement.

An der Taille means at the waist or in the waist area.

German often uses an with clothing-related fit or pressure points on the body:

• an der Taille = at the waist
• an den Schultern = at the shoulders
• an der Brust = at the chest

This tells you where the fit is too tight.

Because an here is followed by the dative case.

The phrase is describing a location: where is the fit too tight?
Answer: at the waist.

Since Taille is feminine:

• nominative: die Taille
• dative: der Taille

So:

• an der Taille = at the waist

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

• dative for a location
• accusative for movement toward something

Here there is no movement. The sentence describes a state or location:

• the fit is too tight at the waist

So German uses the dative:

• an der Taille

Compare:

• Die Jacke ist an der Taille zu eng. = The jacket is too tight at the waist.
• Ich ziehe den Gürtel an die Taille. = I pull the belt toward the waist.
  That second idea involves direction, so it would use accusative.

Eng means tight or narrow.
Zu eng means too tight.

The word zu is used before an adjective to mean too in the sense of excessively:

• zu groß = too big
• zu klein = too small
• zu lang = too long
• zu eng = too tight

So zu eng expresses that the fit is more tight than is acceptable or comfortable.

Because eng is being used predicatively, after the verb sein.

In German, adjectives after sein, werden, or bleiben usually do not take adjective endings:

• Die Hose ist eng.
• Die Jacke ist zu eng.

But before a noun, they do take endings:

• eine enge Hose
• die enge Jacke

So:

• Die Passform ist ... eng. ✅
• Die Passform ist ... enge. ❌

Yes, in der Taille is possible in some contexts, and learners may hear both. But an der Taille is very natural when talking about how clothing fits at a specific body area.

A rough difference is:

• an der Taille = at the waist area
• in der Taille = in the waist/waist section

With clothing and fit, an der Taille is very idiomatic and common.

Usually not in this sentence.

Um die Taille means around the waist, which focuses more on something physically going around the waist, such as:

• a belt
• a rope
• an arm

Examples:

• Sie trägt einen Gürtel um die Taille.
• Er legte den Arm um ihre Taille.

But when describing how a garment fits in a body area, an der Taille is more natural.

Yes, but it is somewhat more common in:

• clothing descriptions
• fashion
• tailoring
• product descriptions

In everyday speech, people may also say things involving die Hüfte or simply describe the clothing directly, but Taille is completely normal and useful when talking about fit.

Examples:

• Die Taille ist zu weit.
• Das Kleid sitzt gut an der Taille.

Mostly yes, or for anything where fit is being discussed in a clothing-like sense.

Passform strongly suggests the way an item fits a body or shape, so it is especially common with:

• clothes
• shoes
• helmets
• gloves

For general tightness without focusing on fit, German might use other wording.

Yes. German is flexible, and you can move the location phrase to the front for emphasis:

• An der Taille ist die Passform zu eng.

This still follows the verb-second rule:

• An der Taille = position 1
• ist = position 2

The meaning stays basically the same, but the waist area gets more emphasis.

The main change would be the subject and the verb.

For example:

• Die Passformen sind an der Taille zu eng.

But in real life, German speakers would often mention the clothing item itself instead of using Passformen:

• Die Hosen sind an der Taille zu eng.
• Die Kleider sind an der Taille zu eng.

Notice:

• singular: ist
• plural: sind

A very useful pattern is:

[subject] + ist/sind + an + dative body area + zu + adjective

Examples:

• Das Hemd ist an den Schultern zu eng. = The shirt is too tight at the shoulders.
• Die Hose ist an den Beinen zu weit. = The trousers are too loose in the legs.
• Das Kleid ist an der Brust zu eng. = The dress is too tight at the chest.
• Die Jacke ist an den Ärmeln zu kurz. = The jacket is too short in the sleeves.

This is a very practical structure for talking about clothing fit in German.