Det är en månatlig kostnad.

Yes, det often means it, and in this sentence it works very much like English it in It is a monthly cost.

Here, det is a dummy subject: a subject word that fills the normal subject position even when we are really just identifying or describing something.

So:

• Det är en månatlig kostnad. = It is a monthly cost.

In real context, det could refer to something already mentioned, like a service, subscription, or charge.

This is the normal Swedish word order for a simple statement:

• Det = subject
• är = verb
• en månatlig kostnad = complement

So the pattern is:

• Subject + verb + rest

That is the standard structure in Swedish main clauses, just like in English:

• It is a monthly cost.

Är means is / are / am, depending on context. It is the present tense of the verb vara, which means to be.

Examples:

• Jag är trött. = I am tired.
• Det är dyrt. = It is expensive.
• De är här. = They are here.

So in your sentence:

• Det är en månatlig kostnad. = It is a monthly cost.

Because kostnad is an en-word in Swedish, also called a common gender noun.

Swedish nouns belong to one of two grammatical genders:

• en-words
• ett-words

Since kostnad is an en-word, you say:

• en kostnad = a cost

Not:

• ett kostnad ❌

This is something you mostly have to learn with each noun.

Because the adjective must agree with the noun it describes.

Here, kostnad is:

• an en-word
• singular
• indefinite

So the adjective takes the basic en-word singular indefinite form:

• en månatlig kostnad

Compare:

• en månatlig kostnad = an en-word, singular, indefinite
• ett månatligt abonnemang = an ett-word, singular, indefinite
• månatliga kostnader = plural
• den månatliga kostnaden = definite form

So månatlig is the correct form because it matches en kostnad.

Månatlig means monthly.

It comes from månad meaning month, plus the adjective-forming ending -lig.

So:

• månad = month
• månatlig = monthly

It describes something that happens every month or is charged every month.

Yes. Swedish often also uses forms with månads-, especially in compounds.

For example, you may see:

• en månatlig kostnad
• en månadskostnad

These are similar, but not always used in exactly the same way.

A rough difference:

• månatlig kostnad = a cost that occurs monthly
• månadskostnad = monthly cost / cost per month, as a compound noun

Both can be natural depending on context.

Kostnad usually means cost, expense, or sometimes charge, depending on context.

Possible translations include:

• cost
• expense
• fee
• charge

For example, in a billing or subscription context, English might translate it more naturally as:

• It is a monthly fee
• It is a monthly charge

So even if the direct meaning is cost, the best English word can change depending on the situation.

Because en is the indefinite article for en-words, like English a/an.

So:

• en kostnad = a cost

With the adjective included:

• en månatlig kostnad = a monthly cost

If it were definite, Swedish would change the structure:

• den månatliga kostnaden = the monthly cost

So en tells you the noun phrase is indefinite: a monthly cost, not the monthly cost.

The definite version would usually be:

• Det är den månatliga kostnaden. = It is the monthly cost.

Notice what changes:

1. en becomes den
2. månatlig becomes månatliga
3. kostnad becomes kostnaden

This is very common in Swedish definite noun phrases:

• en stor bil = a big car
• den stora bilen = the big car

So:

• en månatlig kostnad
• den månatliga kostnaden

No, not in a normal statement. Swedish usually needs an explicit subject in a main clause.

So you need:

• Det är en månatlig kostnad. ✅

Not:

• Är en månatlig kostnad. ❌

You could leave out the subject only in very informal notes, headings, or fragments, but not in a complete standard sentence.

A rough pronunciation guide for an English speaker is:

• Det är en månatlig kostnad
• roughly: deh ehr en MOH-naht-lig KOST-nahd

A few notes:

• ä sounds somewhat like the vowel in English bed, though not exactly.
• å sounds roughly like the vowel in more for many learners, but Swedish pronunciation varies by dialect.
• The g in månatlig is not always pronounced as a strong English g sound in connected speech.
• Swedish has pitch accent, which English speakers usually do not need to master immediately to be understood.

The most useful stress pattern for learners is:

• MÅnatlig
• KOSTnad

The forms are:

• en kostnad = a cost
• kostnaden = the cost
• kostnader = costs
• kostnaderna = the costs

Example:

• Det är flera månatliga kostnader. = There are several monthly costs.

Learning the full noun pattern is very helpful in Swedish, since articles and adjective endings interact with it.