De ligner hinanden.

Not necessarily. De is capitalized simply because it is the first word of the sentence.

In this sentence, de means they.

Danish does also have a formal De meaning you, but at the beginning of a sentence you cannot tell just from the capital letter. You need context. In De ligner hinanden, the presence of hinanden strongly points to they, because hinanden means each other.

The dictionary form is at ligne, meaning to resemble.

Ligner is the present tense form. Danish present tense verbs usually end in -r:

• jeg ligner
• du ligner
• han/hun ligner
• vi ligner
• de ligner

Unlike English, Danish verbs do not change in the present tense depending on the subject. So ligner stays the same for I, you, he, we, they.

Hinanden means each other or one another.

It is a reciprocal pronoun, used when two or more people or things do something mutually. In this sentence, it shows that the resemblance goes both ways.

So hinanden is the word that makes the sentence mean they resemble each other, not they resemble someone/something else.

Because Danish uses the verb at ligne for this idea.

English often says:

• They look like each other
• She looks like her mother

Danish often uses ligne instead:

• De ligner hinanden
• Hun ligner sin mor

So ligne already includes the idea that English expresses with look like or resemble.

Usually no. De ligner by itself often feels unfinished.

It means something like They resemble ... and makes the listener expect more information, unless the context already makes the object obvious.

Adding hinanden makes the meaning complete:

• De ligner hinanden = they resemble each other

Without hinanden, the sentence does not clearly say who or what they resemble.

Yes, in normal usage it is used when the meaning is reciprocal, so it requires at least two participants.

That is why it works with plural subjects such as:

• de
• vi
• I

For example:

• Vi kender hinanden = we know each other
• De hjælper hinanden = they help each other

You would not normally use hinanden with a singular subject, because one person cannot do something to each other.

Yes. De ligner hinanden can be used about people, animals, objects, buildings, pictures, and so on.

For example, it could mean:

• two sisters resemble each other
• two dogs look alike
• two houses have a similar appearance

So the sentence is very general.

Yes. A very common alternative is De ser ens ud.

That means They look the same or They look alike.

The difference is small, but there is a slight nuance:

• De ligner hinanden focuses on resemblance between them
• De ser ens ud focuses on their appearance seeming the same

In many everyday situations, both are possible.

You change the word order for a question, and you add ikke for negation.

• Ligner de hinanden? = Do they resemble each other?
• De ligner ikke hinanden. = They do not resemble each other.

This is useful because it shows the normal Danish statement order here:

• De = subject
• ligner = verb
• hinanden = object/complement

It is the most common everyday choice.

You may also see hverandre, which means the same thing. However, hinanden is generally more common in modern everyday Danish, so it is the safest word to learn first.