In phonetics, stress is a term used to refer to the “degree of force used in producing a syllable.” It may also concern the emphatic articulation of a word within a sentence, as in: “I must go!”

In dealing with words, it may concern a verb or one of the following grammatical units: noun, adjective, preposition, etc. Technically, stress might concern more than one syllable, and a sentence or word may get a primary—as well as a secondary—stress. For the sake of simplicity, here only primary stress is discussed.

NOTE: In the following discussions, ^| = stress.

1. In nouns, adjectives, prepositions, adverbs, etc., the stress is invariably on the last syllable of the word, for example, خانه xāneˈ ‘house, home,’ مدرسه madreseˈ ‘school,’ بزرگ bozoˈrg ‘big, great,’ خراب xarāˈb ‘broken, dysfunctional,’ از aˈz ‘of, from,’ با bā ‘with’ (in monosyllabic words the vowel takes the stress, anyway), بالا bālāˈ ‘up, over, above,’ پایین pāyiˈn ‘down, below.’If an enclitic is added at the end of any of these words, the stress remains on the word, for example, خانه ام
   xāne ˈ- am ‘my house,’ کتابی ketāˈbi‘a book,’ حسن را دیدم hasaˈn rā diˈdam ‘I saw Hasan,’
   کشور ایران kešvaˈr-e irāˈn‘(the country of) Iran’ (this form does not exist in English; but it may be compared with “the city of Berkeley” vs. “Berkeley”).

   If a suffix is added, the suffix takes the stress, for example, حیوان خانگی heyvāˈn-e xāne-giˈ ‘a house pet,’ نصیحت پدرانه nasihaˈt-e pedarāneˈ ‘a fatherly advice,’ آبشارها ābšār hāˈ ‘(the) waterfalls,’ درختان da/eraxtā ˈn ‘trees.’

2. In verbs, the infinitives of all forms (simple, complex, compound) the stress is on the last syllable, for example, دیدن dīdaˈn ‘to see,’ رفتن raftaˈn ‘to go,’ برداشتن bar.dāštaˈn ‘to pick up,’ گوش دادن guš dādaˈn or گوش کردن guš kardaˈn‘to listen.’ The می mī particle takes the stress, for example, می روم mīˈ ravam ‘I go,’ می رفت mīˈ raft ‘(s)he, it was going, used to go.’

   In the progressive variation with the auxiliary verb داشتن dāštan, still [mī] takes the stress, for example, دارم می روم dāram mīˈ ravam ‘I am going,’ داشتم می رفتم dāštam mīˈ raftam ‘I was going.’

   The negative/preventive ﻨﹶ na– prefix takes the stress, for example, نمی روم naˈmī ravam ‘I do not go,’ نمی رفت naˈ mī raft ‘(s)he, it was not going, was not used to go, used not to go’; !نرو naˈro ‘don’t go!’.

   The imperative/subjunctive prefix ﺒ be– takes the stress, for example, !بگو beˈgū! ‘say! tell!’; باید بروم bāyad beˈravam ‘I must go.’

   In the past tense, the stress is on the vowel of the last syllable of the verbal stem, for example, رفتم raˈftam ‘I went,’ برگشتم bargaˈštam ‘I returned.’

   In compound verbs the stress is invariably on the last syllable of the non-verbal element of the compound, for example, !پاشو pāˈ šo ‘get up!’ لازم دارم lāzeˈm dāram ‘I need,’ ساعتم خراب شد sā’atam xarāˈb šod ‘my watch got broken,’ زمین خوردم zamīˈn xordam ‘I fell (down).’

   In the present and past perfect the past participle takes the stress, for example, رفته ام rafteˈam ‘I have gone,’ رفته بودم rafteˈ budam ‘I had gone’; مدرسه را بسته اند، اما می شود از کتابخانه اش استفاده کرد madrese rā basteˈ and, ammā mī šavad az ketābxāne-aš estefāde kard ‘they have closed the school, but it is still possible to use its library’; خانه را خراب کرده بودند، اما هنوز هم قابل استفاده بود xāne rā xarāˈb karde būdand, ammā hanūz ham qābel-e estefāde būd ‘they had ruined the house, but it was still useful.’

   In the classic/formal variation of the future tense, the auxiliary verb خواستن xāstaˈn takes the stress on its last syllable, for example, خواهم رفت xāhaˈm raft ‘I shall go,’ خواهید آمد xāhīˈd āmad plural, ‘you will come.’ (With a stronger stress [as in “I definitely will…”] definitiveness and inevitability is expressed, for example, خواهید آمد xāhiˈˈd āmad ‘you shall (definitely) come,’ خواهیم آمد xāhīˈˈm āmad ‘we will positively come.’