In Altai language the accusative case answers the questions КЕМДИ? (whom), НЕНИ? (of what). This case marks the direct object which is acted upon by the subject. For example in the sentence “They play football” they is a subject, and football is the direct object because it is the thing being done.
So, the principal meaning of the accusative is to designate a person or thing to whom or which on the action is being done, for example: мен ӱредичиди сакып јадымI’m waiting for the teacher.

All the affixes of the accusative case are stressed, except for the words borrowed from another languages.
The affixes of the accusative case are -НЫ, -ДЫ, -НИ, -ДИ, -ТЫ, -ТИ. To put nouns into accusative correctly you should follow the Vowel Harmony rules which state that one word can have only the hard vowels or only the soft vowels.

Here we provide rules to form accusative case from nominative singular nouns.

When the noun ends with a hard back vowel (а, у, ы, о) add any of the affixes -НЫ, -ДЫ, it doesn’t make a difference in meaning. There are several dialects of the altai language, some dialects use –НЫ, and some use –ДЫ. Have a look at the following examples: бакады/баканы тутпаdon’t touch the frog;
бозогоды/бозогоны арчысlean the threshold.

In case the noun ends in a soft front vowel (е, и, ӱ, ӧ) add any of the suffixes -НИ, -ДИ. It depends on the dialect which one of them to choose. Look at examples:
Бу кижиди/кижини айлыҥа кычырinvite this person to your home;
Бу кӧчӧди/кӧчӧни ичeat this pearl-barley soup

You choose only the affix -ДЫ, -ДИ after the voiced consonants (й, л, м, н, ҥ, р) at the end of the noun: карды кӱреshovel the snow, койды азыра – feed the sheep;
малды сугарwater the cattle;
талды кесhew the willow;
кӧлди кечире јӱсswim across the lake;
кайыҥды кесhew the birch;
кӱлди чыгарtake out the ash;
койды кыркыshear the sheep;
кӱнди сакыwait for the sun;
јерди касdig the ground.

In case the noun ends with a voiceless consonant we add affixes –ТЫ, or –ТИ according to the Vowel Harmony rules: касты јунshampoo the goose;
чанакты тарт – pull the sledge;
чачты тараcomb the hair;
айакты јунwash the cup;
эрмекти бичиwrite down the phrase;
бичикти кычырread the book;
чечекти сугарwater the flower;
ийтти божотrelease the dog.

The question КЕМДИ? (whom?) is referred only to people, about animals we ask НЕНИ? (what?)

When we talk about indefinite things or people in general, we use noun in nominative form, for example: бичикa book, бичиктиthe book:
мен кече бичик кычыргамI read a book yesterday
бу бичикти мен кычыргамI have read this book (this concrete book).

Самараa letter, самараны/самарады – the letter:
кече мен самара алгамyesterday I got a letter. – билерим, ол самараны мен бичигем сегеI know, I wrote this letter to you (the concrete letter).

Концертconcert, концерттыthe certain concert:
таҥэртен мен телевизорло концерт кӧргӧмI have seen a concert on TV this morning. – Мен ол корцертты база кӧргӧмI saw this concert too (the same concert).

So, if there are demonstrative pronouns БУ (this, these), ОЛ (that, those) before a noun the nouns become definite, therefore after these words the noun always have the accusative affix.

Personal pronouns in accusative

The pronouns МЕН, СЕН, ОЛ drop their last consonants when forming the accusative case before the accusative affixes –НЫ, -НИ: мени (me), сени (you), оны (him/her/it).

Nominative      Accusative
мен   I мени   me
сен    you сени    you
ол    he/she/it оны    him/her/it
бис    we бисти    us
слер    you (pl) слерди    you (pl)
олор    they олорды    them