Persian verbs have two simple stems and one compound stem. The simple stems are past stem and present stem. Old Persian has several compound stems but modern Persian has only one compound stem called causative stem. Verbal stems are used in conjugating verbs, making participles and also, in word formation. For example, past stem is used to conjugate verbs in past simple tense and present stem is used to conjugate verbs in present simple tense.

Past Stem

The past stem of a verb is obtained by removing -an from its infinitive form.

InfinitivePast Stem
رفتن
raftan
رفت
raft
گفتن
goftan
گفت
goft
آمدن
âmadan
آمد
âmad
خوردن
khordan
خورد
khord

Present Stem

In Old Persian, verbs have various stems that derive from the same root. For example, by adding -a to the root bar (to take), we get the present stem bara and by converting the root to its weak form i.e. bərə and adding -ta to it, we get the past stem bərəta. The relation between a root and its stems has been lost in the transition of Old Persian to Middle Persian and consequently, to New Persian. Therefore, there is no formula for obtaining the present stem of a verb from its infinitive form. Knowing about verb formation and classification of irregular verbs can help you in learning and memorizing present stems.

Each verb whether regular or irregular has one and only one present stem for all persons. Therefore, as opposed to languages like French and Spanish, Persian does not have irregular conjugations. The following table shows the conjugation of دیدن (didan: to see) in present tense. Its present stem بین (bin) is irregular but its conjugation is regular:

می‌بینم
mibinam
I see
می‌بینیم
mibinim
We see
می‌بینی
mibini
You see (informal)
می‌بینید
mibinid
You see
می‌بیند
mibinad
He/She sees
می‌بینند
mibinand
They see

There is a regular rule for obtaining the present stem of a verb but it is only useful for native speakers: consider the imperative form of the verb and drop the prefix ب (and the intermediary consonant ی, in case it exists).

VerbImperativePresent Stem
نوشتن
neveshtan
to write
بنویس
benevis
نویس
nevis
یافتن
yâftan
to find
بیاب
biyâb
یاب
yâb
آمدن
âmadan
to come
بیا
biyâ
آ
â
رفتن
raftan
to go
برو
berow
رو
rav

Causative Stem

The causative stem of a verb is obtained by adding -ân to its present stem. Not all verbs have a causative stem. It is formed only for verbs that can have a causative meaning.