Маленькая рыбка плавает в аквариуме.

The small fish is swimming in the aquarium.

Breakdown of Маленькая рыбка плавает в аквариуме.

• маленький: small
• в: in
• плавать: to swim
• аквариум: the aquarium
• рыбка: the fish

Questions & Answers about Маленькая рыбка плавает в аквариуме.

Why is it маленькая рыбка and not маленький рыбка?

Because рыбка is grammatically feminine, and the adjective has to agree with it.

• The noun рыба (fish) is feminine.
• рыбка is a diminutive of рыба, and it keeps the same gender: also feminine.
• Feminine singular adjectives in the nominative case usually end in -ая / -яя.

So:

• маленьк
  • ая → маленькая (feminine, singular, nominative)
• If the noun were masculine, you’d use маленький (masc. singular nominative), e.g. маленький кот (a small cat).

Because рыбка is feminine, маленькая is the correct form.

What is the difference between рыба and рыбка? Can I always use рыбка for “fish”?

рыба is the basic word for “fish.”
рыбка is the diminutive form, built with the suffix -к-.

Typical nuances of рыбка:

• physically small fish (like an aquarium fish)
• affection / cuteness (“little fishy”)
• more informal, often used with children or about pets

You cannot always replace рыба with рыбка:

• Neutral / serious contexts: use рыба
  
  • Мы ели рыбу. – We ate fish. (not usually рыбку here)
• Talking about pets or small fish in an aquarium: рыбка is very natural:
  • У меня дома живёт маленькая рыбка.

In this sentence, рыбка sounds natural because an aquarium fish is small and often seen as cute or like a pet.

What case is рыбка in, and how do we know it’s the subject?

рыбка is in the nominative singular feminine form.

Clues:

• The basic dictionary form is рыбка – that is also nominative singular.
• The adjective маленькая is also nominative singular feminine, agreeing with it.
• In a simple sentence, the nominative noun is usually the subject.

So маленькая рыбка is the subject, and плавает is the verb (the action the subject does).

What tense/aspect is плавает, and should I translate it as “swims” or “is swimming”?

Плавает is:

• present tense
• 3rd person singular
• imperfective aspect
• of the verb плавать (“to swim”)

Russian present imperfective can correspond to both English:

• “swims” (habitual, general)
• “is swimming” (right now, ongoing)

So Маленькая рыбка плавает в аквариуме can be translated as either:

• “The little fish swims in the aquarium.” (general description)
• “The little fish is swimming in the aquarium.” (current action)

Context decides which English version fits better. Russian itself doesn’t distinguish those two forms here.

What is the difference between плавает and плывёт?

Both come from verbs meaning “to swim / to float”, but they belong to a special pair of motion verbs:

• плавать – multidirectional / repeated / general motion
• плыть – unidirectional motion (in one direction at a given moment)

плавает (from плавать) is used for:

• general ability or habitual action:
  
  • Он хорошо плавает. – He swims well.
• movement in various directions or “swimming around”:
  
  • Рыбка плавает в аквариуме. – The fish is (swimming around) in the aquarium.

плывёт (from плыть) is used when you feel a specific direction or a one-time movement:

• Рыбка плывёт к поверхности. – The fish is swimming (moving) toward the surface.

In your sentence, we’re describing the fish just moving around inside the aquarium, not heading to a specific destination, so плавает is the natural choice.

Why is it в аквариуме and not в аквариум?

The preposition в can take two different cases with different meanings:

1. в + prepositional case → location “in / inside”

   • в аквариуме – in the aquarium (where?)
   • This answers the question Где? (“Where?”)

2. в + accusative case → direction “into”

   • в аквариум – into the aquarium (to where? into what?)
   • This answers the question Куда? (“Where to?”)

In your sentence, we’re talking about where the fish is swimming (inside the aquarium), so we use в аквариуме (prepositional, location), not в аквариум (movement into).

What is the base (dictionary) form and the case of аквариуме?

The base form is аквариум – masculine, singular, nominative.

Аквариуме is:

• prepositional case, singular
• used here after в with the meaning “in” (location)

Declension (singular only):

• Nominative: аквариум – the aquarium (as subject)
• Genitive: аквариума – of the aquarium
• Dative: аквариуму – to the aquarium
• Accusative: аквариум – (same as nominative for inanimate nouns)
• Instrumental: аквариумом – with/by the aquarium
• Prepositional: об аквариуме, в аквариуме – about/in the aquarium

So в аквариуме is “in the aquarium” in the prepositional case.

Why doesn’t Russian use a word for “a” or “the” here?

Russian simply does not have articles like a / an / the.

• Маленькая рыбка… can mean “a little fish” or “the little fish”
• в аквариуме can be “in an aquarium” or “in the aquarium”

Definiteness (a/the) is understood from context, word order, and what is already known in the conversation. When translating into English, you choose a or the based on what sounds right in the situation, but in Russian the sentence stays the same.

Can the word order change, for example Рыбка маленькая плавает в аквариуме? How flexible is the word order?

Russian word order is more flexible than English, but there is a neutral pattern, and changing it can change the emphasis or even the structure.

Neutral version:

• Маленькая рыбка плавает в аквариуме.
  
  • маленькая рыбка = “a little fish” (adjective + noun as one phrase)

If you say:

• Рыбка маленькая плавает в аквариуме.

this is unusual and slightly confusing, because рыбка маленькая is read more naturally as “the fish is small” (subject + predicate adjective), and then плавает в аквариуме is extra information. It feels clumsy.

Better alternative word orders:

• Рыбка плавает в аквариуме. – The fish swims in the aquarium.
• В аквариуме плавает маленькая рыбка. – In the aquarium there swims a little fish. (emphasis on in the aquarium)

But the standard way to link “little” and “fish” is adjective before noun: маленькая рыбка.

How do you pronounce each word? Where is the stress?

Stress (capital letters show the stressed syllable):

• Маленькая – ма-ЛЕНЬ-ка-я

  • IPA (approx.): [ˈmalʲɪnʲkəjə]

• Рыбка – РЫБ-ка

  • IPA: [ˈrɨpkə]

• Плавает – ПЛА-ва-ет

  • IPA: [ˈplavəjɪt]

• В аквариуме – в ак-ВАР-и-у-ме

  • аквариуме: ак-ВАР-и-у-ме
  • IPA: [vkɐˈvarʲɪʊmʲɪ] (the в often clings to the next word in speech)

Key points:

• ы in рыбка is a special Russian vowel; it’s not like English “i” or “ee”.
• Unstressed о and а often sound similar ([ɐ]) in normal speech, but the positions of stress above are correct.

How would I say “Little fish swim in the aquarium(s)” in the plural?

For one aquarium, many fish:

• Маленькие рыбки плавают в аквариуме.
  
  • маленькие – plural adjective (nominative)
  • рыбки – plural noun (nominative)
  • плавают – 3rd person plural verb

For many aquariums and many fish:

• Маленькие рыбки плавают в аквариумах.
  
  • в аквариумах – prepositional plural of аквариум (“in the aquariums”)

Why is it в аквариуме and not на аквариуме?

Russian в usually means “in / inside”, while на usually means “on (top of) / on”.

• в аквариуме – the fish is inside the aquarium
• на аквариуме – would mean “on the aquarium” (on its outer surface), which makes no sense for a fish

Places you’re inside:

• в доме (in the house), в комнате (in the room), в коробке (in the box), в аквариуме (in the aquarium)

Places you’re on:

• на столе (on the table), на крыше (on the roof), на стене (on the wall)

So в аквариуме is the only natural choice for a fish living/swimming in an aquarium.