Learn Hardcore Russian: Я кладу книги и тетради отдельно.

Я кладу is the first person singular present tense of the imperfective verb класть, meaning “I am putting” or “I put” (habitual/process).
Я положу is the first person singular future tense of the perfective verb положить, meaning “I will put” or “I am going to put” (emphasizing completion).

Why are книги and тетради in the accusative case, and why do they look like the nominative?

They are direct objects of the verb кладу, so they take the accusative case. Since both книга (feminine) and тетрадь (feminine) are inanimate, their accusative plurals are identical to their nominative plurals: книги, тетради.

What role does отдельно play in the sentence, and why is it at the end?

Отдельно is an adverb meaning “separately.” Placing it at the end emphasizes the result (“I put the books and notebooks separately”). Russian word order is flexible, so you could also say Отдельно я кладу…, but the given order is more neutral.

Could I use a synonym like раздельно or add друг от друга?

Yes. Раздельно is a close synonym: Я кладу книги и тетради раздельно. To stress “apart from each other,” you can say Я кладу книги и тетради отдельно друг от друга.

Why is there no equivalent of “the” before книги or тетради?

Russian has no articles (no “a,” “an,” or “the”). Definiteness or indefiniteness is inferred from context, word order, or additional words like эти (“these”) if needed.

Why not use another verb like ставить or вешать?

Ставить means “to set/stand (something upright),” and вешать means “to hang.” Класть specifically means “to lay” or “to place horizontally,” which fits when you put books and notebooks down on a surface.

Can I expand the sentence to specify where I put them?

Yes. You can add a locative phrase:
• Я кладу книги и тетради отдельно на полку. (“I put the books and notebooks separately on the shelf.”)
• Я кладу книги и тетради отдельно в шкаф. (“I place the books and notebooks separately in the cupboard.””)