Learn Hardcore Russian: Книга содержит полезные слова.

Книга means book. Содержит is the third-person singular form of содержать, which means to contain. Полезные слова translates as useful words.

Why is the adjective полезные in that particular form, and how does it agree with слова?

In Russian, adjectives must agree with their nouns in gender, number, and case. Here, слова is the plural form of слово and functions as the direct object (accusative case) of the verb. Because inanimate nouns have identical nominative and accusative forms in the plural, полезные appears in its standard plural form to match слова.

Why is the verb содержит used in its current form?

The verb содержит is in the third-person singular present tense form of содержать. It agrees with the subject Книга, which is singular. This subject–verb agreement is a fundamental aspect of Russian grammar.

What grammatical case is used for полезные слова, and why does it look the same as the nominative?

Полезные слова serves as the direct object of the verb содержит, so it is in the accusative case. Since слова is an inanimate noun, its accusative form is identical to its nominative form, which is why there is no visible change in the word's ending.

Is the word order in this sentence typical for Russian, and can it be changed?

Yes, the sentence follows a common Subject-Verb-Object (SVO) order—Книга (subject), содержит (verb), полезные слова (object)—which mirrors standard English order. Although Russian allows for flexible word order to emphasize different parts of the sentence, this structure is clear and straightforward for conveying the basic meaning.