What is a pronoun (damir)?

A pronoun stands in place of a noun so you need not repeat it. It always points at someone already known — which is why every pronoun is definite, and why the pronoun is one of the seven categories.

Every pronoun is mabnī. Its ending never changes: هُوَ is هُوَ whether it is a mubtada', a fāʿil, or the ism of إِنَّ. It holds a position in i'rab without ever showing one.

The detached rafa pronouns. These stand alone as their own word, and they are the ones you meet first.

The dual has one form for both genders — which is why the books count these differently. Learn the grid, not the number.

The attached pronouns. These join onto the end of a word and cannot begin a sentence. They attach to all three word types — an ism, a fiʿl or a ḥarf — and their i'rab depends on what they are attached to: nasab on a verb or on إِنَّ, jarr on a noun or after a ḥarf jarr. An attached pronoun in rafa is a different matter — that one is the doer inside the verb, below.

The same كَ is an object in أَكْرَمَكَ and a mudaf ilayh in كِتَابُكَ. One letter, two positions — decided entirely by its host.

The pronoun inside the verb. Within every verb there is a pronoun, and it is rafa, because it is the doer of the verb. Sometimes you can see it — the تُ of كَتَبْتُ, the وا of كَتَبُوا, the نَ of كَتَبْنَ. Sometimes nothing is written at all and the doer is simply understood: كَتَبَ carries a concealed هُوَ, قُمْ a concealed أَنْتَ. Either way the verb never stands without its doer.

The detached nasab pronouns. Built on إِيَّا, these stand alone in a nasab position — most often an object placed before its verb, as in إِيَّاكَ نَعْبُدُ.

إِيَّا is the pronoun; the letters hung on it only mark who is meant and carry no i'rab of their own. That is why إِيَّاكَ نَعْبُدُ is one object placed before its verb.

Two pronouns named for the job they do, not their shape. ضَمِير الْفَصْل is dropped between mubtada' and khabar to settle which of the two you are reading — زَيْدٌ هُوَ الْمُخْلِصُ. ضَمِير الشَّأْن is not a personal pronoun at all: it stands at the head of a sentence meaning “the matter is —”, and the sentence after it is what explains it — قُلْ هُوَ اللَّهُ أَحَدٌ.

A pronoun is an ism, not a particle, and it carries the same four properties as any other noun.

What it does not carry is an ending. Every pronoun is mabnī: هُوَ is هُوَ whether it is a mubtada', a fā'il or the ism of إِنَّ. It holds a position in i'rab without ever showing one.

Are pronouns definite or indefinite?

Always definite, without exception. A pronoun stands for something already known to both speaker and listener, which is why it never takes ال and never takes tanwin.