Аквариумный фильтр уже работает.

The aquarium filter is already working.

Breakdown of Аквариумный фильтр уже работает.

• работать: to work
• уже: already
• аквариумный фильтр: the aquarium filter

Questions & Answers about Аквариумный фильтр уже работает.

Why is аквариумный an adjective instead of using two nouns, like aquarium filter in English?

Russian often uses an adjective + noun structure where English uses noun + noun.

So:

• аквариумный фильтр = aquarium filter
• literally, aquarium-related filter

This pattern is very common in Russian. A few similar examples:

• кухонный стол = kitchen table
• зубная щётка = toothbrush
• зимняя куртка = winter jacket

So аквариумный describes what kind of filter it is.

What case are аквариумный and фильтр in?

They are in the nominative singular.

That is because фильтр is the subject of the sentence: it is the thing that works / is working.

• фильтр is a masculine singular noun
• аквариумный is a masculine singular adjective agreeing with it

So the forms match:

• аквариумный — masculine singular nominative
• фильтр — masculine singular nominative

Why does аквариумный end in -ый?