امس ذهبت إلى السوق مع أمي.

Because أمس means yesterday, and Arabic often puts time expressions at the beginning for context.

So this sentence is literally structured like:

• أمس = yesterday
• ذهبت = I went
• إلى السوق = to the market
• مع أمي = with my mother

This is very natural in Arabic. You could also say:

• ذهبتُ إلى السوقِ مع أمي أمسِ

That also means I went to the market with my mother yesterday. Arabic word order is more flexible than English.

Because Arabic verbs usually already include the subject.

In ذهبتُ, the ending tells you the subject is I. So Arabic does not need أنا here.

• ذهبتُ = I went
• أنا ذهبتُ = I went too, but أنا adds emphasis

So the sentence does not need أنا unless you want to stress I.

This is a very common beginner question, because normal Arabic writing usually leaves out short vowels.

Without full vowel marks, ذهبت could represent:

• ذَهَبْتُ = I went
• ذَهَبَتْ = she went

The difference is in the final short vowel, which is usually not written.

So in fully vocalized form, your sentence would be:

• أَمْسِ ذَهَبْتُ إِلَى السُّوقِ مَعَ أُمِّي

Since the meaning has already been given to the learner, we understand it here as I went.

إلى means to.

It is the normal preposition used to show movement toward a place:

• ذهبتُ إلى السوق = I went to the market
• ذهبتُ إلى المدرسة = I went to school
• ذهبتُ إلى البيت = I went home / to the house

So إلى is required here because the verb ذهب often takes إلى when you say where someone went.

السوق means the market, while سوق means a market.

So:

• إلى السوق = to the market
• إلى سوقٍ = to a market

In many everyday situations, Arabic often uses the definite form when talking about a familiar or expected place, just like English often says the market, the school, the bank, and so on.

أمي means my mother.

It is made from:

• أم = mother
• ـي = my

So:

• أم = mother
• أمي = my mother

This attached ـي is called a possessive suffix. Arabic often shows possession this way instead of using a separate word like my.

Because أمي already means my mother, and possessed nouns in Arabic normally do not take ال.

So Arabic says:

• أمي = my mother
  not
• الأمي

The possession suffix ـي already makes the noun specific.

مع means with.

So:

• مع أمي = with my mother

It is used to show accompaniment:

• مع صديقي = with my friend
• مع أبي = with my father
• مع المعلم = with the teacher

A fully vowelled version is:

• أَمْسِ ذَهَبْتُ إِلَى السُّوقِ مَعَ أُمِّي

This helps show the grammar and pronunciation more clearly:

• أَمْسِ = yesterday
• ذَهَبْتُ = I went
• إِلَى = to
• السُّوقِ = the market
• مَعَ = with
• أُمِّي = my mother

In normal Arabic writing, these short vowels are usually omitted.

In standard Arabic, the usual spelling is أمس with a hamza on أ.

So the standard form is:

• أمس

You may sometimes see امس in casual or less careful writing, but for Modern Standard Arabic, أمس is the better spelling to learn and use.