Har De glemt Deres medlemskort, eller ligger det stadig i tasken fra i går?

They are the formal forms of you and your in Danish.

• De = formal you
• Deres = formal your

They are often capitalized to distinguish them from:

• de = they
• deres = their

So this sentence is addressing someone politely, not casually.

A native speaker would very often say:

Har du glemt dit medlemskort, eller ligger det stadig i tasken fra i går?

Changes:

• De → du
• Deres → dit

That is because du is the usual informal you in modern Danish. The formal De exists, but it sounds quite formal, old-fashioned, or especially polite.

Har De glemt is the present perfect, formed with:

• har = have
• glemt = forgotten

So literally it is Have you forgotten...

This is very natural when talking about something with present relevance: the person does not have the card now.

Glemte De is the simple past, more like Did you forget... It is possible in some contexts, but har glemt fits very well here.

Glemt is the past participle of glemme (to forget).

The pattern is:

• infinitive: at glemme
• present: glemmer
• past: glemte
• past participle: glemt

In this sentence, it is used with har to make the perfect tense: har glemt.

Because Danish usually does not use an article when there is a possessive.

So:

• medlemskortet = the membership card
• Deres medlemskort = your membership card

You do not normally say both the possessive and the definite article together in this kind of phrase.

Because Danish, like German, commonly makes compound nouns by writing them as one word.

Here:

• medlem = member
• kort = card

Together:

• medlemskort = membership card

The s in the middle is a linking sound that often appears in compounds.

Because medlemskort is a neuter noun.

In Danish, nouns are either:

• common gender
• neuter

Et kort means a card, so kort is neuter. That means the pronoun referring back to it is det.

So:

• et kort → det
• en taske → den

That is why the card is referred to as det.

Danish often uses a position verb where English would simply say is.

• ligger literally means lies or is lying
• but it is also commonly used for something being located somewhere, especially an object resting in a place

So:

ligger det stadig i tasken?
= is it still in the bag?

This sounds natural in Danish because the card is thought of as physically lying in the bag.

Because this part is also a question.

In Danish yes/no questions, the finite verb usually comes first:

• statement: Det ligger stadig i tasken.
• question: Ligger det stadig i tasken?

So after eller, the speaker asks a second possible question:

• Har De glemt ...
• eller ligger det stadig ...

This is a choice between two possibilities.

Stadig means still.

In this sentence:

ligger det stadig i tasken?
= is it still in the bag?

Its position is normal in Danish. In a question with inversion, the order is often:

• verb
• subject
• adverb
• rest of sentence

So:

• ligger = verb
• det = subject
• stadig = adverb

Fra i går literally means from yesterday.

Here it belongs with tasken:

tasken fra i går
= the bag from yesterday

So the idea is: the bag that was used yesterday, or the bag associated with yesterday.

It does not mean the card is physically dating from yesterday. It describes the bag.

Because eller here joins two clauses:

• Har De glemt Deres medlemskort
• eller ligger det stadig i tasken fra i går

In Danish writing, a comma is often used before a conjunction when it connects full clauses. So the comma helps mark the two alternatives clearly.

It presents two possible explanations:

1. You forgot your membership card
2. It is still in yesterday’s bag

So the speaker is not really asking two unrelated questions. They are asking which of the two possibilities is true.

In English, we often do the same thing:

Did you forget your membership card, or is it still in yesterday’s bag?