Volontären är kär.

Because Swedish usually marks definiteness on the noun itself by adding an ending.

• volontär = a volunteer
• volontären = the volunteer

The ending -en is the definite singular ending for many common-gender nouns.

In Swedish, the is often built into the noun instead of being a separate word.

So:

• volontären = the volunteer

This is one of the biggest differences from English.
You do not normally say a separate the before volontären in a simple sentence like this.

är means is / are / am, depending on the subject in English.

Its infinitive, or dictionary form, is vara, which means to be.

Examples:

• jag är = I am
• du är = you are
• volontären är = the volunteer is

Unlike English, Swedish uses the same present-tense form är for all persons.

This is the normal basic word order in a Swedish main clause:

subject + verb + complement

So:

• Volontären = subject
• är = verb
• kär = complement

This is very similar to English:

• The volunteer is in love

kär is an adjective.

In this sentence it is used after the verb är, so it is a predicative adjective. That means it describes the subject through the verb to be.

So Volontären är kär means that the volunteer has the quality of being in love.

Swedish adjectives often change form depending on gender, number, and sometimes whether they are used before a noun or after a verb.

Here, volontären is a singular common-gender noun, so the adjective stays in the basic common-gender singular form:

• Volontären är kär = The volunteer is in love

Other forms can appear in other contexts, for example:

• ett kärt barn = a dear/beloved child
• de är kära = they are in love

So kär is the correct form for a singular common-gender subject here.

Not always. kär can mean things like dear, beloved, or fond, depending on context.

But after är, especially when talking about a person, it very often means in love.

For example:

• Hon är kär. = She is in love.
• Han är kär i henne. = He is in love with her.

So in this sentence, in love is the natural interpretation.

Yes. You can add i plus a person or thing.

For example:

• Volontären är kär i Anna. = The volunteer is in love with Anna.

Without that extra phrase, Volontären är kär just means The volunteer is in love, without saying with whom.

A rough guide is:

vo-lon-TEH-ren

A few pronunciation notes:

• ä sounds somewhat like the e in bed, though not exactly the same.
• The stress is usually on the last syllable of volontär: volon-TÄR
• In volontären, that stressed ä remains important.

A rough English-style approximation might be:

vo-lon-TAIR-en

But it is best to listen to native audio if possible, especially for the vowel ä.

A rough pronunciation is:

shair or kyair, depending on accent and how closely you imitate Swedish pronunciation.

Important points:

• k before ä is pronounced with a sh-like sound in standard Swedish.
• ä is a front vowel somewhat like the e in bed, but longer here.
• r is pronounced in a Swedish way, which varies by region.

So kär does not sound like English car.

It exists and is correct, but in everyday Swedish, frivillig is often more common in many contexts.

Very roughly:

• volontär often sounds a bit more formal, organizational, or role-based
• frivillig can often be the more everyday choice

Still, volontären är kär is perfectly good Swedish.

Yes. Then you would use the indefinite form of the noun:

• En volontär är kär. = A volunteer is in love.

Compare:

• Volontären är kär. = The volunteer is in love.
• En volontär är kär. = A volunteer is in love.

So the main difference is whether you are talking about a specific known volunteer or just any volunteer.

Yes. Just like in English, context decides how you understand it.

• It can describe the volunteer’s current emotional state: The volunteer is in love
• It can also be part of a larger story or description

Swedish does not require a special form here to show that distinction. The plain present tense är works naturally.