"уже" or "ещё"

Compound conjunction → ...то, что... / ...тот, кто...

Почему? or Зачем?

"который"

Superlative degree of adjectives

Comparative degree of adjectives

"Если..." or "Если бы..." - conditional mood

"Что" or "Чтобы"

Prepositions of purpose

Prepositions of place

Prepositions of time

Modality: я могу, я способен, это возможно...

"человек" vs "люди"

 Foreigners often ask how and when it is correct to say "человек" and "люди". It's pretty simple. "Человек" is the singular form, and "люди" is the plural form. But there are nuances (details) that you need to know.

Modality: ты должен, вам надо...

гнать - гонять

тащить - таскать

катить - катать

Prefixed motion verbs - what is important to know

Constructions with the word "есть"

Могу. Умею. Знаю. / I can. I'm able to. I know.