На обед я приготовил чечевицу и рис.

This is because the direct objects are in the accusative case.

• чечевица is a feminine noun, so in the accusative singular it changes:
  • nominative: чечевица
  • accusative: чечевицу
• рис is a masculine inanimate noun, and masculine inanimate nouns usually have the same form in the accusative as in the nominative:
  • nominative: рис
  • accusative: рис

So after приготовил (prepared/cooked), both nouns are objects, but they behave differently because of their gender and declension pattern.

Приготовил is the perfective past form of приготовить, while готовил is the imperfective past form of готовить.

Here, приготовил is used because the speaker is talking about a completed result: the lunch was prepared.

• Я приготовил чечевицу и рис. = I prepared / cooked lentils and rice.
• Я готовил чечевицу и рис. = I was cooking / used to cook lentils and rice, or it focuses more on the process rather than the completed result.

Russian often uses the perfective when the action is seen as a finished whole.

На обед literally means something like for lunch or for the lunch meal.

In Russian, на + accusative is often used to mean for a meal, occasion, or purpose.

Examples:

• на завтрак = for breakfast
• на обед = for lunch
• на ужин = for dinner

So На обед я приготовил чечевицу и рис means For lunch, I prepared lentils and rice.

This is a very natural Russian pattern. English speakers sometimes expect something like для обеда, but на обед is the normal everyday expression.

Yes, я can be omitted.

Russian often leaves out subject pronouns when the verb form already makes the subject clear.

• Я приготовил чечевицу и рис.
• Приготовил чечевицу и рис.

Both can work, depending on context.

However, я may be included:

• for emphasis
• for clarity
• because the speaker wants to contrast themselves with someone else

For example:

• Я приготовил, а не он. = I prepared it, not him.

So in your sentence, я is not required, but it is perfectly natural.

Yes. Приготовил shows that the speaker is masculine.

In the past tense, Russian verbs agree with gender in the singular:

• masculine: приготовил
• feminine: приготовила
• neuter: приготовило

So:

• Я приготовил чечевицу и рис. = said by a man
• Я приготовила чечевицу и рис. = said by a woman

This is one of the first places where Russian past tense differs a lot from English.

Yes, Russian word order is flexible.

The sentence На обед я приготовил чечевицу и рис is natural, with на обед placed first to set the context: as for lunch / for lunch.

Other possible orders include:

• Я приготовил на обед чечевицу и рис.
• Чечевицу и рис я приготовил на обед.

These all mean roughly the same thing, but the emphasis changes:

• На обед... puts the meal context first
• Я приготовил... emphasizes the subject or action first
• Чечевицу и рис... emphasizes what was prepared

Russian word order often reflects focus and emphasis, not just grammar.

Russian has no articles.

So Russian nouns do not normally include words corresponding to a, an, or the.

• чечевицу could mean lentils, some lentils, or the lentils
• рис could mean rice, some rice, or the rice

The exact meaning depends on context.

English speakers often want to know which article is intended, but in Russian this is usually left unstated unless context makes it specific.

Yes, рис is singular, but it is a mass noun, like English rice.

Mass nouns refer to substances or materials rather than countable individual items. So Russian normally says:

• рис = rice not a plural form for the food in general

Likewise, чечевица can also be used as a mass noun meaning lentils as food, even though English often uses the plural lentils.

So the Russian grammar here is normal:

• чечевицу и рис = lentils and rice

Yes. In Russian, чечевица is often treated as a singular noun when referring to the food in general.

That is different from English, where lentils is usually plural.

So:

• чечевица = lentils / lentil dish / lentil food in general

This is a vocabulary difference, not a mistake. Languages often package food words differently.

In this sentence, for lunch is the best translation.

• На обед я приготовил чечевицу и рис. = I prepared lentils and rice for lunch.

If you translated it as at lunch, that would sound more like it describes the time when the cooking happened, which is not the main idea here.

Russian на обед usually answers the question for what meal?, not when?

So it is about purpose or intended meal:

• for breakfast
• for lunch
• for dinner

Yes. Both nouns are direct objects of приготовил.

The structure is:

• приготовил = prepared/cooked
• чечевицу и рис = lentils and rice

The conjunction и simply links the two objects:

• чечевицу
  • и
    • рис

So the verb applies to both:

• he prepared lentils
• he prepared rice

This is the same basic idea as in English I prepared lentils and rice.