To form simple sentences like “I want a dog”, you need to use the accusative case. The Russian accusative case is used for the object of a sentence, in this case the word “dog”. The only time we use the accusative case in English is with pronouns. We use “me” instead of “I” and “him” instead of “he”. The Russian language uses the case for all nouns.

The accusative case is also used after the prepositions “в” (to, into) and “на” (on, to) when they indicate motion towards something.

Definition: An “animate” noun is something that is alive and can move by itself. People or animals (not plants). An “inanimate” noun is a non-living object.

Here are the rules for forming the accusative case from the dictionary (nominative) form.

Masculine Nouns:

1. If the noun in inanimate, there is no change.
2. If noun is animate and ends in a consonant, add “а”.
3. If noun is animate, replace “й”, with “я”.
4. If noun is animate, replace “ь”, with “я”.

Feminine Nouns:

1. Replace “а” with “у”.
2. Replace “я” with “ю”.
3. Does not change if a soft sign.

Neuter Nouns:

1. Inanimate nouns do not change (almost all neuter nouns are inanimate).

Forming Plurals

For plural nouns the accusative case just 'borrows' from the other cases, depending on whether the object is animate or not.

Inanimate nouns (not-alive) : Same as the nominative plural.
Animate nouns (alive) : Same as the genitive plural.

Personal Pronouns Of The Accusative Case

Here are the Russian pronouns that can be used as the object of a sentence. (Accusative case)

Меня - Me

Тебя - You (informal)

Его ("yevo") - Him

Её - Her

Нас - Us

Вас - You (formal, or plural)

Их - Them

Pronouns that start with vowels may be proceeded by the letter "н" when used with some prepositions.

Русский язык для иностранцев в Алматы

Источник: russianlessons.net