Learn Hardcore Icelandic: Hann er leiður þegar hann missir uppáhalds leikfangið sitt. - He is sad when he loses his favorite toy.

Leiður is an adjective meaning roughly sad / sorry / fed up, and in Icelandic adjectives agree with the gender, number and case of the noun (or pronoun) they describe.

Hann (he) is masculine singular nominative, so the adjective takes the masculine nominative singular form leiður.
With hún (she), which is feminine, you would say hún er leið.
With það (it), which is neuter, you would say það er leitt.

So:

Hann er leiður. – He is sad.
Hún er leið. – She is sad.
Barnið er leitt. – The child is sad. (child = neuter word)

The -ur / zero / -tt pattern (leiður / leið / leitt) is very common for adjectives in Icelandic.

Does leiður mean sad or bored? When would I use it instead of other words like dapur or leiðinlegur?

Leiður is usually used about a person’s feeling, and it most often means:

sad / upset
sorry
fed up / tired of something (emotionally)

Examples:

Ég er svo leiður yfir þessu. – I’m so sad/sorry about this.
Hún er orðin leið á verkefninu. – She is fed up with the project.

Compare:

leiðinlegur – boring, annoying (used for things or situations)
- Þessi bíómynd er leiðinleg. – This movie is boring.
dapur – sad, gloomy (more “poetic” or serious)
- Hann var dapur eftir fréttirnar. – He was sad after the news.
sorgmæddur – grief-stricken, very sad
- Hún var sorgmædd eftir missinn. – She was grief-stricken after the loss.

So in the sentence Hann er leiður þegar hann missir uppáhalds leikfangið sitt, leiður is the normal everyday way to say sad / upset about what happened.

Why is the word order þegar hann missir and not þegar missir hann?

In Icelandic, main clauses are often verb-second (V2): the finite verb tends to come in the second position:

Hann missir leikfangið sitt. – He loses his toy.
Í dag missir hann leikfangið sitt. – Today he loses his toy.

However, in subordinate clauses introduced by words like þegar (when), að (that), af því að (because), etc., the normal order is:

conjunction + subject + verb + rest

So:

þegar hann missir uppáhalds leikfangið sitt – when he loses his favorite toy

and not:

✗ þegar missir hann uppáhalds leikfangið sitt

That second version sounds wrong in standard Icelandic except in very special, marked contexts. So your sentence uses the expected subordinate-clause word order.

Both verbs are in the present: Hann er leiður þegar hann missir…. Does this mean it’s happening right now, or “whenever” he loses the toy? How would I say it for one specific event in the past?

With þegar and both verbs in the present, the Icelandic sentence usually means:

He is (gets) sad whenever / every time he loses his favorite toy.

So it describes a general or habitual situation, not one single event.

For one specific past event, you would normally use the past tense:

Hann var leiður þegar hann missti uppáhalds leikfangið sitt.
– He was sad when he lost his favorite toy.

Very often Icelandic also uses verða (to become) for the change of state:

Hann varð leiður þegar hann missti uppáhalds leikfangið sitt.
– He became/got sad when he lost his favorite toy.

So:

er… missir → general / habitual: is sad when(ever) he loses…
var / varð… missti → single event in the past: was / became sad when he lost…

Could I use ef instead of þegar, like Hann er leiður ef hann missir uppáhalds leikfangið sitt? What’s the difference?

Yes, you can use ef, but it changes the meaning slightly.

þegar = when / whenever, for something that is assumed to actually happen (or be very likely).
- Hann er leiður þegar hann missir uppáhalds leikfangið sitt.
  → Whenever he loses it, he (in fact) gets sad.
ef = if, for a condition that may or may not happen.
- Hann er leiður ef hann missir uppáhalds leikfangið sitt.
  → If he (ever) loses it, he will be sad. (It’s hypothetical / conditional.)

So þegar talks about a regular, expected situation; ef talks about a possible one.

Where does missir come from? Is it just missa with a different ending, and how is it different from tapar?

Yes. Missa is the infinitive (“to lose”), and missir is the 3rd person singular present:

infinitive: að missa – to lose / drop / miss
1st sg pres.: ég missi – I lose
3rd sg pres.: hann/hún/það missir – he/she/it loses
past sg: hann missti – he lost
past participle: missa → misst

In this sentence, hann missir = he loses.

Difference from tapa:

missa + accusative is used for losing or dropping something you had:
- Hann missti leikfangið sitt. – He lost (dropped / misplaced) his toy.
tapa + dative is used for losing a game, money, etc.:
- Hann tapaði leiknum. – He lost the game.
- Hún tapaði peningum. – She lost money.

So for a toy that he has and then no longer has, missa is the right verb.

Why does leikfangið end in -ið? What form and case is it?

Leikfang means toy and is a neuter noun.

In Icelandic, the definite article (“the”) is usually attached as a suffix to the noun:

leikfang – a toy
leikfangið – the toy

For neuter nouns, nominative and accusative singular are the same form, ending in -ið in the definite:

Nom. sg.: leikfangið – the toy (subject)
Acc. sg.: leikfangið – the toy (object)

In your sentence, leikfangið is the direct object of missir, so it is in the accusative singular, but that happens to look identical to nominative because it’s neuter:

Hann missir uppáhalds leikfangið sitt.
– He loses his favorite toy. (object in acc.)

What exactly does sitt mean, and why don’t we just say leikfangið hans for “his toy”?

Sitt is the reflexive possessive pronoun, the neuter singular form of sinn, sín, sitt.

sinn – masc.
sín – fem.
sitt – neut.

These words:

Refer back to the subject of the same clause (reflexive).
Agree with the noun they modify (in gender, number, case).

In your sentence:

Subject: hann
Noun: leikfangið – neuter, singular, accusative
So you use: sitt – neuter, singular, accusative

Hence: uppáhalds leikfangið sitt – his (own) favorite toy.

If you said:

uppáhalds leikfangið hans, that would normally mean:
- someone else’s favorite toy belonging to him, not necessarily the subject’s own.

Compare:

Hann missti hattinn sinn. – He lost his (own) hat.
Hann missti hattinn hans. – He lost his (another man’s) hat.

So sitt here shows clearly that the toy belongs to the same “he” who is sad.

What is uppáhalds grammatically? Why does it end in -s, and does it change form?

Historically, uppáhalds is the genitive singular of the noun uppáhald (favourite, something you are especially fond of). In modern usage, uppáhalds functions like an indeclinable adjective meaning favorite.

Key points:

The -s you see is historically a genitive ending, but in this use it is fixed; you don’t change it.
Uppáhalds does not change for gender, number, or case.

Examples:

uppáhalds leikfangið mitt – my favorite toy
uppáhalds bókin mín – my favorite book
uppáhalds lögin okkar – our favorite songs

In all of these, uppáhalds stays exactly the same.

Why is it uppáhalds leikfangið sitt and not sitt uppáhalds leikfang? And can uppáhalds and leikfangið be written as one word?

There are two related issues here: word order and compounding.

Word order in the noun phrase

In Icelandic, the typical order is:

(other adjectives) + uppáhalds + noun + definite ending + possessive pronoun

So:

uppáhalds leikfangið sitt
gamla uppáhalds leikfangið mitt – my old favorite toy

Possessive pronouns like minn / þinn / sinn are very often placed after a definite noun:

bíllinn minn – my car
leikfangið sitt – his (own) toy

You can place a possessive before for emphasis or in certain structures, e.g.:

sitt eigið leikfang – his own toy

But for something like “his favorite toy” with a definite noun, the natural order is:

uppáhalds leikfangið sitt, not sitt uppáhalds leikfang.

Compounding

Icelandic happily forms compounds, so you will also see:

uppáhaldsleikfangið sitt

written as one word (except for sitt):

uppáhaldsleikfangið – the favorite toy
uppáhaldsleikfangið sitt – his favorite toy

Both uppáhalds leikfangið sitt and uppáhaldsleikfangið sitt are understandable; the compound form is often more typical in formal or careful writing, since compounds are very common in Icelandic.