Learn Hardcore Swedish: Jag tycker att hennes jacka är fin.

tycker (att …) = to think (have an opinion)
- Jag tycker att hennes jacka är fin. → You’re giving your opinion about the jacket.
tycker om (något) = to like (something)
- Jag tycker om hennes jacka. → I like her jacket (focus on liking it, not on stating an opinion in sentence form).
tror (att …) = to think / to believe (about facts, guesses, beliefs)
- Jag tror att hennes jacka är dyr. → I think (believe) her jacket is expensive (a belief about reality, not really a value judgment like “nice” / “ugly”).

In short:

tycker (att …) → opinion / value judgment
tycker om → liking
tror (att …) → belief about reality or what is true

Is the word att necessary? Can I leave it out like English that?

att in this sentence works like English that in I think that her jacket is nice.

Full form: Jag tycker att hennes jacka är fin.
In casual spoken Swedish, att is often dropped after tycker, so you may also hear:
Jag tycker hennes jacka är fin.

Both are grammatical. However:

In writing and in careful speech, it is safer and more standard to include att.
Unlike English, Swedish generally uses att more consistently; omission is common in speech but less so in formal text.

So: you can omit att here in everyday speech, but including it is always correct and slightly more formal/clear.

Why is it hennes jacka and not hennes jackan?

In Swedish, when you use a possessive pronoun (like min, din, hans, hennes), the noun that follows is indefinite (no -en / -et ending and no separate article):

en jacka → a jacket (indefinite)
jackan → the jacket (definite)
hennes jacka → her jacket (possessive; no en and no -n)

You cannot combine:

a possessive pronoun + the definite form at the same time:
- ✗ hennes jackan (wrong)
- ✓ hennes jacka

The “definiteness” is already expressed by the possessive pronoun (hennes), so the noun stays in its basic indefinite form (jacka).

Why do we use hennes here, and how is it different from sin?

hennes means her / hers and does not change with gender or number of the thing owned:

hennes jacka → her jacket
hennes böcker → her books

Important difference: hennes vs sin:

hennes = her (someone else’s, not the grammatical subject of the clause)
sin / sitt / sina = her/his/their own (refers back to the subject of the clause)

In your sentence:

Jag tycker att hennes jacka är fin.
hennes must refer to some female person who is not “jag” (me).

If the subject were hon, and she is talking about her own jacket:

Hon tycker att sin jacka är fin. → She thinks her own jacket is nice.
Hon tycker att hennes jacka är fin. → She thinks some other woman’s jacket is nice.

So: hennes here tells us it’s another woman’s jacket, not the speaker’s, and not automatically the subject’s if the subject were hon.

Why is it fin and not fint or fina?

Adjectives in Swedish agree with the noun in gender and number.

Base forms of fin (“nice / pretty”):

fin – common gender, singular, indefinite (en-words)
fint – neuter gender, singular, indefinite (ett-words)
fina – plural (both genders) and also definite forms

Since jacka is an en-word (common gender), singular, and here it is indefinite after a possessive (hennes jacka), the correct adjective form is:

en jacka → en fin jacka
hennes jacka → hennes jacka är fin

Other examples:

ett hus → ett fint hus
mina skor → mina fina skor

Why is the word order är fin and not fin är? Could we rearrange it?

In Swedish, the normal word order in such a clause is:

Subject – Verb – Predicate (adjective / noun)

Here, in the subordinate clause introduced by att:

Subject: hennes jacka
Verb (copula): är
Predicate adjective: fin

So the order hennes jacka är fin is standard S–V–(rest).
The order ✗ hennes jacka fin är is incorrect.

Unlike some languages, Swedish does not place the adjective before the verb in this structure. You always need the verb är between the subject and the adjective.

Could I also say Jag tycker om hennes jacka? Is it the same thing?

Yes, you can say:

Jag tycker att hennes jacka är fin.
→ Literally you express an opinion: you judge the jacket as fin.
Jag tycker om hennes jacka.
→ You say you like her jacket.

In everyday conversation, these two often communicate almost the same idea. Nuance:

tycker att … är fin focuses on the opinion/judgment (“I think it’s nice”).
tycker om focuses on liking (“I like it”).

Both are natural, and which one you choose depends on whether you want to stress an opinion (good / bad / ugly / nice) or your personal liking.

How would I make this sentence negative? Where does inte go?

There are two slightly different possibilities, with a difference in focus.

Negate the thinking (I don’t think …):
- Jag tycker inte att hennes jacka är fin.
  → You are denying that you hold the opinion “her jacket is nice”.
Negate the property inside the clause (I think it’s not nice):
- Jag tycker att hennes jacka inte är fin.
  → You specifically think that the jacket is not nice (focus inside the subordinate clause).

Word order rules:

In the main clause, inte usually comes after the finite verb:
Jag tycker inte …
In a subordinate clause, inte comes after the verb:
… att hennes jacka inte är fin.

Most of the time, for “I don’t think her jacket is nice”, you’ll use:

Jag tycker inte att hennes jacka är fin.

How do you pronounce the words in Jag tycker att hennes jacka är fin?

Approximate pronunciation (Swedish standard, very simplified):

Jag → like “yahg” (g often soft/weak)
tycker → roughly “TÜK-ker”
- y is like German ü or French u (fronted “oo” sound)
att → “att” (short a, clear t; often very short in speech)
hennes → “HEN-nes”
jacka → “YACK-a”
- initial j is like English y in “yes”
är → “äär” (like “air” but without the final r sound in many accents)
fin → “feen” (long i as in “machine”)

Swedish has its own rhythm and melody (pitch accent), but for a learner, focusing on the vowel qualities (especially y, ä, i) and the j = y sound in jacka is a good start.

Are there other common ways to express the same idea in Swedish?

Yes, here are a few natural alternatives with slightly different nuances:

Jag tycker om hennes jacka.
→ I like her jacket. (focus on liking)
Jag gillar hennes jacka.
→ I like her jacket. (more informal; gillar is very common in speech)
Jag tycker att hennes jacka är snygg.
→ I think her jacket is stylish / good-looking (snygg can sound a bit more about style/fashion).
Jag tycker att hennes jacka är väldigt fin.
→ I think her jacket is very nice. (adding emphasis with väldigt)

All of these are idiomatic; which one you choose depends on how strong and what type of positive feeling you want to express.