The subject of a verbal sentence is called فَاعِل fā’il. It is the person or thing that does the action.
The subject of a nominal sentence is called مُبتَدَأ Mubtada. It is simply a noun which begins the sentence.
The Fā’il and Mubtada always take the nominative case رَفع raf’.
The subject is highlighted in the following sentences.
اِشتَرى خَالِدٌ السَّيَّارَةَ
Khalid bought the car
رَجَعَ الوَالِدُ مِنَ السُّوقِ
The father returned from the market
الوَلَدُ جَالِسٌ فِي الظِلِّ
The boy is sitting in the shade
The subject can also be shown in the form verb inflections. We will learn more about this in the verb chapters.
أُحِبُّ شُرْبَ القَهوَةِ صَبَاحًا
I like drinking coffee in the morning
I read the book
جِئنَا مِنَ السُّعُودِيَّة
We have come from Saudi
Finally, the Mubtada can also be a pronoun,
هُو في البيتِ
He is in the house
هِي مُدَرِّسَة فِي المَدرَسةِ
She is a teacher at the school
هَذا مَسجِدٌ قَدِيمٌ
This is an old mosque