Для маленькой кухни квадратный стол практичнее, чем круглый стол.

Because для normally requires the genitive case.

• Dictionary form: кухня = kitchen
• After для: для кухни = for the kitchen

So для маленькой кухни means for a small kitchen.

The adjective has to agree with the noun it describes in gender, number, and case.

Here:

• кухня is feminine singular
• after для, it becomes genitive singular
• so маленькая changes to маленькой

That is why you get:

• маленькая кухня = a small kitchen
• для маленькой кухни = for a small kitchen

In Russian, the verb to be is usually omitted in the present tense.

So Russian says:

• Квадратный стол практичнее...

instead of literally saying:

• A square table is more practical...

This is completely normal. Russian often leaves out present-tense is / am / are.

They are in the nominative singular masculine form.

• стол is a masculine noun
• квадратный and круглый agree with стол
• the sentence is talking about a square table and a round table in a general sense

So:

• квадратный стол = square table
• круглый стол = round table

Both noun phrases stay in the nominative here because they are the things being compared.

Практичнее is the comparative form of практичный (practical).

• практичный = practical
• практичнее = more practical

A very important point: this comparative form does not change for gender or number here.

So you can say:

• стол практичнее = the table is more practical
• кухня практичнее = the kitchen is more practical

The word практичнее stays the same.

Чем means than in comparisons.

So:

• практичнее, чем круглый стол = more practical than a round table

This is one of the most common ways to make comparisons in Russian:

• лучше, чем... = better than...
• больше, чем... = more/bigger than...
• быстрее, чем... = faster than...

Yes, in many situations Russian can omit the repeated noun if it is obvious:

• Для маленькой кухни квадратный стол практичнее, чем круглый.

That sounds natural and means the same thing.

But repeating стол is also correct. Repeating it can make the sentence a little clearer, especially for learners or in more careful speech.

So both are possible:

• ...чем круглый стол
• ...чем круглый

Russian word order is flexible, and starting with Для маленькой кухни puts the context first:

• For a small kitchen, a square table is more practical than a round table.

This makes the sentence sound natural because it tells you the situation before giving the main statement.

You could also rearrange the sentence:

• Квадратный стол для маленькой кухни практичнее, чем круглый стол.

This is also understandable, but the original version emphasizes the small kitchen first.

Here it means for, not in.

• для маленькой кухни = for a small kitchen

The idea is suitability: a square table is more practical for that kind of kitchen.

If you wanted to say in a small kitchen, you would normally use a different structure, such as:

• в маленькой кухне = in a small kitchen

So:

• для = for
• в = in

Because the sentence is talking about a small kitchen as a type of situation, not about many kitchens.

Russian often uses the singular when speaking generally:

• Для маленькой кухни... = For a small kitchen...
• Для большой семьи... = For a big family...
• Для ребенка... = For a child...

English does something similar in many general statements.

It is most naturally understood as a general statement:

• A square table is more practical than a round table for a small kitchen.

Russian often uses singular nouns without articles, and context tells you whether it means:

• a square table / a round table in general
• or the square table / the round table in a specific situation

Here, without any extra context, it sounds like a general observation about furniture choices.

Sometimes in natural English, yes, but grammatically it specifically means more practical.

• практичный = practical
• практичнее = more practical

So if you want to stay close to the Russian wording, more practical is the best match.

Here are the basic forms:

• для = for
• маленький = small
• кухня = kitchen
• квадратный = square
• стол = table
• практичный = practical
• чем = than
• круглый = round

In the sentence, some words change form because of grammar, especially маленькой кухни.