Conjugation endings attach to verbal stems to form different tenses for different grammatical persons. There are three grammatical persons in Persian: first person, second person and third person. Each grammatical person can be singular or plural. For example, first person singular (I) and first person plural (we). Therefore, there are six grammatical persons altogether. These grammatical persons can be abbreviated as 1S, 2S, 3S, 1P, 2P, 3P. For example, 2S means second person singular, 3P means third person plural and so on.

There are two sets of conjugation endings: past endings and present endings. They only differ in third person singular (3S):

Past EndingsPresent Endings
1Sم
am
م
am
2Sی
i
ی
i
3S-
-
د
ad
1Pیم
im
یم
im
2Pید
id
ید
id
3Pند
and
ند
and

The past ending for third person singular is null (empty). It means that nothing is added to the stem. An empty ending indicates the person of the verb is third singular because all the other persons have a non-empty ending.

Stress position

Conjugational endings are enclitic. That is, contrary to a suffix, they are unstressed and do not shift the stress position to the last syllable, which is the normal stress position in Persian. Therefore, the stress falls on the preceding syllable. For example, look at the conjugation of نوشتن (neveshtan) in past simple tense.

1Sنوشتم
ne-vesh-tam
I wrote
1Pنوشتیم
ne-vesh-tim
We wrote
2Sنوشتی
ne-vesh-ti
You wrote
2Pنوشتید
ne-vesh-tid
You wrote
3Sنوشت
ne-vesht
He/She wrote
3Pنوشتند
ne-vesh-tand
They wrote

Pronoun-dropping

In English, we can't omit the subject pronoun in "I wrote" and say "wrote" because the person of the verb becomes unclear. In Persian, each person has a unique conjugation ending. That is, conjugational endings convey the person and the number of the verb. For example, in نوشتم (neveshtam), the ending -am indicates that the person of the verb is first person singular (I).

Languages that have this feature are called pro-drop (pronoun-dropping) or more precisely, a null-subject language. In Persian, subject pronouns are not normally used. We say نوشتم (neveshtam) instead of من نوشتم (man neveshtam). The latter is only used when we want to put some emphasis on the grammatical person. Spanish and Italian are also null-subject languages.