Eine Wäscheklammer fehlt noch, deshalb legt meine Schwester das Handtuch erst einmal über den Stuhl.

Because Wäscheklammer is a feminine noun. In the nominative singular, the indefinite article for feminine nouns is eine.

Here, Eine Wäscheklammer is the subject of fehlt, so nominative is required.

It is a compound noun:

• Wäsche = laundry
• Klammer = clip, clamp

So Wäscheklammer literally means a laundry clip. In German compounds, the last part determines the gender, so because Klammer is feminine, Wäscheklammer is also feminine.

A very common pattern in German is that the thing that is missing becomes the subject.

So:

• Eine Wäscheklammer fehlt noch. = a clothespin is still missing

If you want to say who is lacking it, that person is often in the dative:

• Mir fehlt noch eine Wäscheklammer. = I’m still missing a clothespin / I still need a clothespin

That is different from the most natural English structure, so it often feels backwards at first.

Here noch means still or yet.

It shows that the situation has not changed up to this point: the clothespin is still missing.

So fehlt noch gives the idea of is still missing.

Because the sentence contains two main clauses:

• Eine Wäscheklammer fehlt noch
• deshalb legt meine Schwester das Handtuch erst einmal über den Stuhl

In German, two main clauses are often separated by a comma, especially when the second one is introduced by a linking word like deshalb.

Not exactly. Deshalb is best thought of as an adverb or connector meaning therefore, for that reason, or that’s why.

That matters because it does not behave like a subordinating conjunction such as weil. It does not send the verb to the end. Instead, it takes up the first position in the clause, and the finite verb still stays in second position.

So:

• Deshalb legt meine Schwester ...

not

• Deshalb meine Schwester legt ...

German main clauses follow the verb-second rule. That means the finite verb must be in the second position.

In this clause, deshalb takes the first position, so the verb legt must come next. The subject meine Schwester comes after the verb.

Pattern:

• deshalb = position 1
• legt = position 2
• meine Schwester = after the verb

This is very common in German whenever something other than the subject comes first.

Legen means to lay or to put something somewhere, and it is used when placing something in a horizontal position.

That fits das Handtuch well. A towel is something you can legen somewhere.

Also, über den Stuhl legen suggests draping it over the chair. German often uses legen for that kind of placement.

Compare:

• legen = lay, put down
• stellen = stand, put upright
• setzen = set something into a sitting position
• hängen = hang

Handtuch is a neuter noun, so its nominative and accusative singular definite article is das.

In this sentence, das Handtuch is the direct object of legt, so it is in the accusative. For neuter nouns, the article is still das, so there is no visible change here.

Because über is a two-way preposition. It can take either:

• accusative for movement toward a destination
• dative for location

Here, the towel is being moved and placed over the chair, so German uses the accusative:

• über den Stuhl

If you were only describing location, you could use dative in a different kind of sentence, for example:

• Das Handtuch hängt über dem Stuhl.

That means the towel is already hanging over the chair.

Here erst einmal means something like for now, for the time being, or temporarily.

It suggests this is not the final or ideal solution. Since a clothespin is missing, the sister puts the towel over the chair for now.

This expression is very common in spoken and written German when someone does something as a temporary step.

Not with exactly the same meaning.

• auf den Stuhl legen means putting the towel onto the chair
• über den Stuhl legen means laying or draping it over the chair

So über den Stuhl gives the image of the towel hanging across the chair, not simply resting on the seat.

German present tense often covers both simple present and present progressive ideas from English.

So:

• fehlt can mean is missing
• legt can mean puts or is putting

German does not normally need a special progressive form like English is putting, so the ordinary present tense is completely natural here.