Min søster bemærker altid, hvis nogen glemmer et komma.

Because søster is being used in a general possessive phrase: min søster = my sister.

In Danish, when you use a possessive like min, din, hans, vores, etc., the noun usually appears in its basic indefinite form, not with the definite ending.

• min søster = my sister
• søsteren = the sister

So:

• min søster = correct
• min søsteren = not correct in normal Danish

Bemærker is the present tense of bemærke, meaning to notice.

Danish present tense is often formed by adding -r to the infinitive:

• bemærke = to notice
• bemærker = notices / is noticing

So Min søster bemærker altid ... means My sister always notices ...

Unlike English, Danish does not change the present tense according to the subject:

• jeg bemærker = I notice
• du bemærker = you notice
• hun bemærker = she notices

The verb form stays the same.

In a normal main clause, Danish typically puts the finite verb in second position. This is often called the V2 rule.

Here the order is:

• Min søster = subject
• bemærker = finite verb
• altid = adverb

So:

• Min søster bemærker altid ...

This is very natural Danish word order.

Compare with English:

• English: My sister always notices ...
• Danish: Min søster bemærker altid ...

The adverb often comes after the finite verb in Danish main clauses.

Hvis means if here and introduces a subordinate clause:

• hvis nogen glemmer et komma = if someone forgets a comma

It sets up the condition under which the sister notices something.

Be careful: hvis usually means if, not when. In some contexts English may use if or when more flexibly, but Danish hvis is specifically conditional.

Because Danish normally uses a comma before a subordinate clause, especially when it is introduced by words like:

• hvis = if
• at = that
• fordi = because
• som = who/which/that

So in:

• Min søster bemærker altid, hvis nogen glemmer et komma.

the comma marks the start of the subordinate clause.

This is more regular and visible than in modern English, where such commas are often omitted.

It is also slightly funny or self-referential that the sentence is about forgetting a comma and itself contains a comma.

Here nogen means someone.

In Danish, nogen can be tricky because it can mean different things depending on context:

• nogen = someone / anyone
• nogle = some, a few

In this sentence:

• hvis nogen glemmer et komma = if someone forgets a comma

So nogen is being used as an indefinite pronoun meaning someone.

Examples:

• Er der nogen hjemme? = Is anyone home?
• Nogen ringede. = Someone called.
• Jeg har nogle bøger. = I have some books.

So here it is definitely the someone/anyone meaning, not some.

Because subordinate clauses in Danish usually do not follow the same word order pattern as main clauses.

In the subordinate clause:

• hvis = subordinator
• nogen = subject
• glemmer = verb
• et komma = object

So the normal order is:

• hvis nogen glemmer et komma

This is similar to English: if someone forgets a comma.

A useful contrast:

• Main clause: Min søster bemærker altid ...
• Subordinate clause: hvis nogen glemmer et komma

In Danish, the verb-second rule applies to main clauses, not in the same way to subordinate clauses.

Because komma is a neuter noun in Danish, so it takes et.

Danish nouns are common gender or neuter:

• en for common gender
• et for neuter

So:

• et komma = a comma

Other examples of neuter nouns:

• et hus = a house
• et ord = a word

You usually just have to learn the gender with each noun.

Yes. Glemmer literally means forgets, from the infinitive glemme.

In this sentence, it most naturally means something like:

• forgets to put
• leaves out by mistake
• omits because they forgot it

So hvis nogen glemmer et komma is understood as if someone forgets a comma or more naturally in English, if someone forgets to include a comma.

Danish often lets the object stand directly after glemme in cases like this, even if English might express the idea with an extra phrase.

Yes. Danish allows fronting, but then the finite verb still stays in second position in the main clause.

For example:

• Altid bemærker min søster, hvis nogen glemmer et komma.
  This is grammatical, but less natural and more marked.

• Hvis nogen glemmer et komma, bemærker min søster det altid.
  This is also grammatical, but now the structure is changed a little and det is useful to refer back to the whole situation.

The original sentence is the most natural neutral version:

• Min søster bemærker altid, hvis nogen glemmer et komma.

Yes, a few things:

• sø in søster contains the Danish vowel ø, which does not exist in standard English.
  It is a rounded front vowel. English speakers often replace it with something like sir or suh, but neither is quite right.

• søster is roughly pronounced with the stress on the first syllable.

• bemærker has stress on mær:

  • be-MÆR-ker

• The letter r in Danish is usually softer and more back in the mouth than a typical English r.

• Final syllables in Danish are often less strongly pronounced than in English.

Even if your pronunciation is not perfect, getting the stress roughly right helps a lot:

• SØster
• beMÆRker

Because the content is about noticing when someone forgets a comma, and the sentence itself contains a comma before hvis.

So there is a small self-referential joke or irony in it:

• the sister notices punctuation mistakes
• and the sentence demonstrates punctuation at the same time

A native speaker might feel that it sounds like something said about a very language-aware or grammar-conscious person.