There are some points to note about these pronouns:
The third person singular pronoun “او” is used only for humans. For non-humans, the pronoun “آن” is used instead.
In polite or formal speech, individuals are addressed with plural pronouns. Using verbs in plural form in such situations is also common.
In literal texts, as you might guess, the third person plural pronoun (آنها) can be replaced by “آنان” when being used for humans.
All of the pronouns listed above can actually serve as different parts of speech such as subject, object, object of preposition, etc.
آنها دوستان من بودند.
او با ما جنگید.
They were my friends.
He/She fought with us.
Enclitic Personal Pronouns
Enclitic pronouns are always attached to other words as suffixes and are never pronounced with a stress.
Enclitic pronouns are used in two different ways. (Notice that using enclitic pronouns is always optional since free personal pronouns can always replace them.)
Enclitic pronouns attach to nouns to indicate possession.
In many occasions, including when showing emphasis on the owner, using free pronouns is more common.
As you see, here again, two vowels cannot be pronounced right after each other. If the word ends with letter “ه” with an “e” sound, a glottal stop with letter “ا” is used (as in “خندهاش”). If the last letter of the word is “ا” with an “aa” sound, the letter “ی” with a “y” sound comes in between (as in “صدایشان” and “دروغهایتان”). Obviously, if a noun has a plural mark such as “ها” and “ان”, the enclitic pronouns come after the plural mark (as in “دروغهایتان”).
The object of a verb can be shown by suffixing the verb itself with an enclitic pronoun.
روی میز گذاشتمش.
به یک اتاق تاریک بردندمان.
پدر خندید و بوسیدشان.
دیروز در خیابان دیدمت.
من پختمش و تو خوردیش.
I killed him.
I put it on the table.
They took us to a dark room.
Father laughed and kissed them.
I saw you in the street yesterday.
I cooked it and you ate it.
As you probably noticed in the beginning, some of these enclitic pronouns are identical with past simple verb suffixes. This can be source of problems; what is the meaning of the word “زدم”? Does it mean “I hit” consisting of the past stem and the first person singular subjective suffix? Or does it mean “he hit me” formed of the past simple verb “زد” meaning “he/she hit” plus the first person singular objective pronoun “م”? The answer is quite simple. It is definitely the first one. Generally, in cases like this where such ambiguities are feared, enclitic pronouns are not used and objects come as free personal pronouns, in a manner which will be discussed under objects. (Note again that using enclitic pronouns is always optional. However, it takes time to grasp a feeling of when it sounds more natural to use them and when it does not.)
Place and Direction
Enclitic pronouns can also follow words indicating place and direction.
پایم رفت رویش.
بیرون خانه قشنگ بود امّا تویش زشت بود.
I trampled on it. (lit. My foot went on it)
Outside the house was beautiful but inside it was ugly.