Þessi jakki er of þröngur á öxlunum, en hinn er alltof víður.

Þessi means this, so Þessi jakki = this jacket.

Hinn means the other one / the latter one / that other one, depending on context. In this sentence, hinn refers to another jacket already understood from the situation:

• Þessi jakki = this jacket
• hinn = the other one

So the contrast is:

• This jacket is too tight at the shoulders,
• but the other one is much too wide.

Because both adjectives describe jakki, which is:

• masculine
• singular
• nominative

In Icelandic, adjectives must agree with the noun they describe in gender, number, and case.

So:

• jakki is masculine singular nominative
• therefore the predicate adjectives are also masculine singular nominative:
  • þröngur = tight/narrow
  • víður = wide/loose

If the noun were feminine or plural, the adjective form would change.

Here of means too.

So:

• of þröngur = too tight / too narrow

This is a very common Icelandic pattern:

• of stór = too big
• of lítill = too small
• of dýr = too expensive

Be careful not to confuse this of with English of. They are unrelated in meaning.

Both express excess, but alltof is stronger.

• of þröngur = too tight
• alltof víður = much too wide / far too wide

So alltof adds extra emphasis. You can think of it as:

• of = too
• alltof = much too / far too

In this sentence, the second jacket is not just wide, but really too wide.

Á öxlunum means at the shoulders / on the shoulders.

The noun is öxl = shoulder. Here it appears as öxlunum, which is:

• dative plural
• with the definite article attached
• literally: the shoulders

So:

• á öxlunum = on/at the shoulders

This is a natural way in Icelandic to say a garment is tight in that part of the body.

Because the preposition á often takes the dative when it expresses location rather than motion.

Here the jacket is tight at the shoulders — a static location — so Icelandic uses dative:

• á öxlunum

Also, it is plural because we normally talk about shoulders, not just one shoulder.

So the structure is:

• á
  • dative plural
• öxlunum = the shoulders

In Icelandic, the definite article is usually attached to the end of the noun, instead of being a separate word like English the.

So:

• axlir = shoulders
• axlirnar = the shoulders
• öxlum = shoulders (dative plural, indefinite)
• öxlunum = the shoulders (dative plural, definite)

That is why öxlunum already includes the meaning of the shoulders.

Because Icelandic normally includes the verb again in the second clause:

• Þessi jakki er of þröngur á öxlunum
• en hinn er alltof víður

This is the natural full structure: this jacket is... but the other one is...

In English, we also usually repeat is:

• This jacket is too tight..., but the other one is much too loose/wide.

So the repeated er is completely normal.

Literally, víður means wide. But when talking about clothes, English often prefers loose depending on context.

So in this sentence, alltof víður could be understood as:

• much too wide
• far too loose

If you are translating naturally rather than word-for-word, too loose may sound more idiomatic in English for clothing.

Sometimes yes, but in this sentence the other one is usually better.

Hinn often refers to the second of two known items. Since one jacket has already been mentioned, hinn points to the other jacket.

Possible translations:

• the other one ← best here
• that one ← possible in some contexts
• the latter ← more formal/literary

So here:

• en hinn er alltof víður = but the other one is much too wide

It can absolutely mean tight for clothing.

The basic idea of þröngur is narrow / tight / cramped, and the best English translation depends on context.

Examples:

• þröng gata = a narrow street
• þröngt herbergi = a cramped room
• jakki er þröngur = the jacket is tight

So in this sentence, of þröngur á öxlunum is naturally understood as too tight at the shoulders.

The structure is:

• Þessi jakki = subject
• er = verb
• of þröngur = adjective phrase
• á öxlunum = prepositional phrase
• en = but
• hinn = subject of the second clause
• er = verb
• alltof víður = adjective phrase

So the overall pattern is:

[This jacket] [is] [too tight] [at the shoulders], but [the other one] [is] [much too wide].

This is a very typical Icelandic sentence pattern and closely matches English word order.