Speakers of English should find learning Persian to be easier than learning Arabic. Persian has no grammatical gender, for instance. It has no case endings or noun-adjective agreement. Its morphology is concatenative (prefixes and suffixes are stacked on to roots in a linear fashion), like English, with none of the dreaded “root and pattern” syndrome of Arabic, except in loanwords. Persian makes no distinction like the “verb forms” of Arabic or the “binyanim” of Hebrew. What complications Persian does present are very similar to those found in English and mainly concern the verb system: verbs have a 2x3 number by person conjugation, have separate past and non-past stems, and have a large number of composite tenses that are formed by stacking participles and auxiliary verbs.
However, similarities between Arabic and Persian are great enough that no study of Persian will be complete without covering some aspects of Arabic as well. Speakers of Persian are often unaware of just what elements of their language are Arabic in origin. Students of Persian, however, may benefit by recognizing the Arabic element of Persian as something distinct, since it is governed by slightly different rules.
It follows that anyone who already knows Arabic is at an advantage when studying Persian. However, such students should beware of so-called “false friends.” There are many words and grammatical elements of Arabic origin that have taken on a different usage in Persian. Assuming that they are “the same” as in Arabic in every way can lead to unnecessary mistakes.
Since it is quite common in the United States for students to arrive at Persian after having at least some exposure to Arabic, some of the potential short cuts, as well as false friends, will be mentioned.
The Persian alphabet contains all 28 letters of the Arabic alphabet plus an additional four:

Each of these letters is ordered in the dictionary immediately after the Arabic letter it is modified from.
There are eight Arabic letters that are used only in the spelling of Arabic loanwords. These are the six so-called guttural consonants
and the two interdental fricatives:
. None of these letters are pronounced the way they are in Arabic. This actually makes pronunciation of Persian much easier than pronunciation of Arabic. Each of these sounds is pronounced the same was an already existing Persian sound in the following way:

No matter how long it took you to learn to pronounce all of these letters correctly in Arabic, you will have to retrain yourself to pronounce them “incorrectly” in Persian. This shouldn't take as long. Persian speakers tend to have little appreciation for the differences these letters are supposed to make in Arabic, and often wonder why there are four letters that are all “z.”
The Arabic consonant
is pronounced v in Persian.
Finally, the letters
both represent the same sound in Persian, which is closer to the sound made by in
Arabic, like a throaty French or German “r.” Neither letter is restricted in Persian to Arabic loanwords, but there is no reason to worry about pronouncing them differently. Thus, the Arabic loanwords
“near” and
“strange” are both pronounced gharib in Persian.
A very symmetrical relation exists between the six vowels of Persian and the three vowels of classical Arabic. Arabic a (fatha) is Persian a when short and Persian a when long. Arabic i (kasra) is Persian e when short and Persian i when long. Arabic u (dammah) is Persian o when short and Persian u when long. Thus, Arabic murshid “guide” is Persian morshed, because both vowels are short in Arabic. However, Arabic mudir “director” is Persian modir because the i is long in Arabic. There are hardly any exceptions to this pattern. As long as you remember what vowels are short in Arabic, you can predict the pronunciation in Persian very well. Arabic geminate consonants (shaddah) are also preserved in loanwords into Persian, which are thus likewise predictable if you know your Arabic. Be forewarned, however, that native Persian words may also have geminate consonants.
Also, very important: all Persian words are stressed on the last syllable, no matter how they are stressed in Arabic. No exceptions.
3.3 The Arabic root and pattern system
Students of Semitic languages like Arabic will be aware of the fact that related words are often derived by means of the root and pattern system. The root word s-l-m is a commonly used example. From the basic verb salima, to be safe, Arabic derives other verbs such as sallama, to hand over or deliver; aslama, to submit; and istaslama, to surrender. The nouns salam, peace; salama, health or safety; and muslim, a Muslim, derive from the same root.
Being an Indo-European language, Persian does not derive words in this manner, but by means of affixation, which is far more intuitive to English speakers. Thus, from the Persian root saz “healthy,” we have sazgar “wholesome,” sazesh “collusion,” nasaz “discordant,” nasazgari “unwholesomeness,” etc.
Arabic words that have been derived in Arabic by means of the root and pattern system are borrowed into Persian one at a time and undergo the predictable sound changes that all Arabic sounds undergo when borrowed into Persian. Persian speakers probably simply learn these words individually with poor understanding of how they are derived in Arabic. However, if you understand the Arabic root and pattern system, you can use it as a shortcut to figuring out how these words should be pronounced in Persian. The root and pattern system guarantees that all words generated according to a single pattern all have the same vowels. This uniformity will remain even after the word is borrowed into Persian, since all the vowels will change in the same way. Thus, all words of Arabic origin that have the pattern
are guaranteed to be pronounced tafa'ol in Persian. If you encounter a word in print and recognize it as a member of an Arabic pattern, you do not have to look it up to know how it is pronounced in Persian. This will work even for Arabic words you've never seen before, as long as you recognize what pattern they are derived from, and remember the rules of Arabic-to-Persian sound correspondence.
The Arabic root and pattern system is also used to derive plural forms of nouns in ways that seem strange and unpredictable to non-Arabic-speakers. For instance, the plural of kitab “book” is kutub “books.” Many Arabic words have been borrowed into Persian together with their plural forms. Persian dictionaries will list these words and their Arabic plurals separately. In other words, you do not have to figure out what the “root” of the word is in order to look it up. Persian speakers often do not use the Arabic plural forms and create new ones by adding one of the Persians plural suffixes
to the Arabic singular form. Thus, Arabic
“member” is borrowed into Persian as ozv and its plural
“members” is borrowed as a'za'. However, in the course of time Persian speakers have created their own plural
ozvha. Both plural forms are in use in Persian, sometimes even within in the same text. Both forms are acceptable in speech and in writing. The name of the infamous taliban of Afghanistan is similarly derived. It is in fact the Arabic word talib “student” suffixed with the Persian plural suffix –an. The actual Arabic plural of talib is tullab.
The Arabic grammatical construct known as idafa has a counterpart in Persian known as ezafe. The name “ezafe” is of course simply the Persian pronunciation of the Arabic word idafa (the guttural d becomes z, the short a becomes e, etc.). However, despite the name and other similarities, Arabic idafa and Persian ezafe are really two different grammatical constructs. Students of Arabic who are learning Persian should not assume that they automatically understand ezafe. While some uses of the two constructs overlap, Persian ezafe is far more powerful and broadly used. For instance, any Persian adjective and the noun it modifies stand in an ezafe relationship. This is never the case with Arabic idafa.
Some instances of Arabic idafa have been borrowed into Persian as entire phrases. For instance, Arabic
“impending, imminent” has been borrowed into Persian as gharib-elvoghu'. The internal idafa structure of phrases like this is grammatically opaque in Persian. The Persian word “ayatollah” is similarly from the Arabic idafa
“signs of God.” Its structure is also opaque in Persian.
The large number of Arabic loanwords in Persian is of course welcome news to those with prior knowledge of Arabic. This can indeed help you, so don't let it trip you up instead. You will often see “Arabic” words appear in Persian texts spelled exactly as they would be in Arabic. Make sure you do not pronounce them as they are pronounced in Arabic! Failure to modify the vowels correctly and shift stress to the last syllable may result in the word as you pronounce it not even being recognized by Persian speakers. Failure to degutturalize the guttural consonants may result in Persian speakers thinking something is wrong with your throat and offering you a glass of water.
A final word of warning concerns words whose Persian meaning has shifted somewhat from their Arabic meaning. For instance, Arabic musamaha means “forgiveness” while its Persian cognate mosamaha means “negligence.” Many differences are more subtle. No matter how well you know Arabic, check to make sure what the usage of an Arabic loanword is in Persian before you start using it yourself.