Um leið og þvotturinn er búinn, hengir hún fötin á þvottasnúruna.

Um leið og is a very common Icelandic time expression meaning as soon as, the moment that, or when in the sense of one thing happening immediately after another.

So in this sentence, it introduces the event that happens first, and the main clause tells you what happens next.

• Um leið og þvotturinn er búinn = as soon as the laundry is done
• hengir hún fötin á þvottasnúruna = she hangs the clothes on the clothesline

It is a fixed expression, so it is best learned as a whole.

Þvotturinn means the laundry, while þvottur means just laundry or washing in a more general sense.

The ending -inn is the attached definite article, which in Icelandic is usually added onto the noun instead of being a separate word like English the.

So:

• þvottur = laundry
• þvotturinn = the laundry

Here, the sentence is talking about a specific load of laundry, so the definite form makes sense.

Búinn here is part of the expression vera búinn, which often means to be finished, to be done, or to have completed something, depending on context.

In this sentence:

• þvotturinn er búinn = the laundry is done / finished

The word búinn is an adjective/participle, and it agrees with the noun it describes:

• þvotturinn is masculine singular nominative
• therefore the form is búinn (masculine singular nominative)

You might also see:

• Hún er búin = she is finished / she has finished
• Verkið er búið = the work is finished

So the ending changes depending on gender and number.

This is because Icelandic follows a verb-second pattern in main clauses.

When the sentence begins with something other than the subject, the finite verb still usually comes second. Here, the sentence starts with the time clause:

• Um leið og þvotturinn er búinn

After that introductory element, the main clause begins, and the verb comes before the subject:

• hengir hún fötin á þvottasnúruna

So:

• neutral main-clause order: Hún hengir fötin á þvottasnúruna
• after an introductory clause: Um leið og ..., hengir hún fötin ...

This is very normal Icelandic word order.

Fötin is the accusative plural definite form here, because it is the direct object of hengir.

She is hanging the clothes, so the clothes are what receives the action.

A useful thing to know is that föt is normally a plural noun in Icelandic. You usually do not use a singular form in everyday meaning.

So:

• föt = clothes
• fötin = the clothes

In this sentence, fötin is the object, so accusative is expected.

In normal usage, yes, föt is generally treated as a plural noun meaning clothes.

That is similar to English, where clothes is also plural in form. Icelandic often talks about clothing this way:

• föt = clothes
• fötin = the clothes

So a learner should get used to seeing plural agreement and plural forms with this word.

This is about how Icelandic uses case after some prepositions, including á.

With á, the case often depends on whether there is:

• movement toward a place/surface → accusative
• location on a place/surface → dative

Here, the clothes are being moved onto the clothesline, so Icelandic uses the accusative:

• á þvottasnúruna = onto the clothesline

If you were describing location instead, you would expect dative:

• Fötin eru á þvottasnúrunni = the clothes are on the clothesline

So this is a very important accusative-vs-dative pattern in Icelandic.

Þvottasnúra means clothesline or washing line.

It is a compound noun:

• þvotta- relates to washing/laundry
• snúra = cord, line, string

So literally it is something like laundry-line.

In the sentence, it appears as þvottasnúruna, which is the definite accusative singular form:

• þvottasnúra = a clothesline
• þvottasnúruna = the clothesline

Icelandic often uses the present tense in sentences like this when describing:

• habits
• routines
• general truths
• actions understood from context as happening in the future

So:

• er búinn
• hengir

can sound very natural even if English might sometimes prefer something like will hang in certain contexts.

In a sentence about routine behavior, the present tense is especially natural:

• as soon as the laundry is done, she hangs the clothes on the line

So this is not strange Icelandic at all.

Yes. This is a very useful point.

Vera búinn að + infinitive often means that someone has finished doing something.

For example:

• Hún er búin að þvo fötin = she has finished washing the clothes

But in your sentence, there is no að + infinitive. Instead, the phrase simply means that the laundry itself is finished:

• Þvotturinn er búinn = the laundry is done

So there are two related patterns:

• vera búinn = be finished / be done
• vera búinn að + infinitive = have finished doing something

These two letters are very important in Icelandic.

• þ is like the th in English thing
• ð is like the th in English this

From the sentence:

• þvotturinn
• þvottasnúruna

both begin with þ, so they start with the thing sound, not a t sound.

The word leið contains ð, which is the softer this sound.

So roughly:

• þ = voiceless th
• ð = voiced th

This distinction is one of the first pronunciation habits English speakers need to build in Icelandic.

Yes. Everything in it is very natural and everyday:

• Um leið og is a common way to express immediate sequence
• þvotturinn er búinn is a normal way to say the laundry is done
• hengja föt á þvottasnúruna is ordinary household vocabulary

So this is a good model sentence for learning several useful patterns at once:

• time clause + main clause
• verb-second word order
• definite noun endings
• accusative after motion with á
• the expression vera búinn