امي تقول إن الطبخ مع اختي اسهل.

Because in careful Standard Arabic spelling, three things are usually added:

• Hamza at the beginning of words like أمي, أختي, and أسهل
• Shadda on إنّ
• Sometimes full vowel marks in teaching materials

So a more formal version is:

أمي تقول إنّ الطبخ مع أختي أسهل

In everyday typing, many native speakers leave out hamzas and other diacritics, so امي تقول إن الطبخ مع اختي اسهل is very common online, even though it is less formal.

The suffix -ي means my.

So:

• أم = mother
• أمي = my mother

and

• أخت = sister
• أختي = my sister

This is a very common way Arabic shows possession.

Because when a noun takes a possessive suffix like -ي meaning my, it is already definite.

So Arabic does not use ال together with that suffix.

Correct:

• أختي = my sister

Not correct:

• الأختي

This is similar to how English would not say the my sister.

إنّ means that.

In this sentence:

• أمي تقول = my mother says
• إنّ الطبخ مع أختي أسهل = that cooking with my sister is easier

So the whole sentence means:

• my mother says that cooking with my sister is easier

Grammatically, إنّ also affects the structure of the clause after it. It makes the following noun its subject, and that noun is formally in the accusative case. Here that is الطبخَ, although the case ending is usually not written in normal text.

Because الطبخ is a verbal noun, often called a masdar. It means cooking.

So:

• الطبخ = cooking
• أطبخ = I cook

Arabic often uses a verbal noun where English also uses an -ing form.

So الطبخ مع أختي means:

• cooking with my sister

rather than

• I cook with my sister

Those are different ideas.

In Arabic, the present-tense verb to be is usually omitted.

So Arabic says:

• الطبخ مع أختي أسهل

literally something like:

• cooking with my sister easier

but the meaning is:

• cooking with my sister is easier

This is completely normal in Arabic nominal sentences.

Because أسهل is the comparative form, meaning easier.

• سهل = easy
• أسهل = easier

So:

• الطبخ مع أختي سهل = cooking with my sister is easy
• الطبخ مع أختي أسهل = cooking with my sister is easier

In this sentence, أسهل compares cooking with the sister to some other situation, even if that comparison is only understood from context.

A fully vocalized version is:

أُمِّي تَقُولُ إِنَّ الطَّبْخَ مَعَ أُخْتِي أَسْهَلُ

A few useful notes:

• أُمِّي = my mother
• تَقُولُ = says
• إِنَّ = that
• الطَّبْخَ = cooking, formally accusative after إنّ
• مَعَ = with
• أُخْتِي = my sister
• أَسْهَلُ = easier

In normal writing, these short vowels are usually omitted.

Because مع أختي is a prepositional phrase that belongs with الطبخ and helps specify what kind of cooking is being talked about.

So the structure is roughly:

• الطبخ = cooking
• مع أختي = with my sister
• أسهل = easier

Together:

• cooking with my sister is easier

Arabic often places this kind of phrase between the topic and the description very naturally.

They are related, but they are not always interchangeable.

In this sentence, after تقول, إنّ is the natural choice for reported speech:

• أمي تقول إنّ... = my mother says that...

Learners often confuse إنّ and أنّ because both can be translated as that, but they are used in different grammatical environments. For this sentence, إنّ is the expected form.

It breaks down like this:

• أمي = my mother
• تقول = says
• إنّ = that
• الطبخ = cooking
• مع أختي = with my sister
• أسهل = easier

So the grammar is:

1. Main clause: أمي تقول

   • subject: أمي
   • verb: تقول

2. Reported clause after إنّ: الطبخ مع أختي أسهل

   • الطبخ = the topic or subject of the clause
   • مع أختي = attached prepositional phrase
   • أسهل = predicate

A natural English gloss is:

• my mother says that cooking with my sister is easier