This is the 1753rd most frequent Arabic word.
the
In Arabic, "the" corresponds to "أل" (Al-), a definite article used to indicate specificity.
In this sentence, 'ال' is the definite article in Arabic, equivalent to 'the' in English, used to specify the nouns 'الكتاب' (the book) and 'الطاولة' (the table).
الكتاب على الطاولة.
The book is on the table.
In this context, 'ال' specifies 'الحديقة' (the garden), differentiating it as a particular garden.
ذهبت إلى الحديقة مع أصدقائي.
I went to the garden with my friends.
Here, 'ال' is used to define 'الرجل' (the man) and 'الأستاذ' (the teacher), indicating specific individuals.