There are two particles used as suffixes to verbs to express emphasis in Arabic or to give an assertive tone to a certain action. Those particles are the emphatic nūn (ـنَّ/ـنْ) and the emphatic lām (لَـ).

Emphatic nūn / نُون التَوْكِيد

The emphatic nūn (نون التوكيد) is a letter nūn (ـن) suffixed to a verb to emphasize the action it expresses. This noun can be found under two different versions at the end of the verb; the heavy version and the light version, although the heavy version is most often preferred:

• The heavy nūn (نُون التَوكِيد الثَقِيلة) is a nūn bearing a shadda and a fatḥa ـنَّ (most used)
• The light nūn (نُون التَوكِيد الخَفِيفة) is a nūn bearing the sukūn ـنْ

Conditions of use

Both the heavy nūn and the light nūn are suffixed to verbs under the same conditions. The verb has to be:

Imperative or interdiction:

Write the sentence on the board	اُكْتُبَنَّ الجُمْلةَ على اللَوْحِ
Don’t open the gift now	لا تَفْتَحَنْ الهَدِيّةَ الآنَ

In the present tense:

• In the negative form

He doesn’t live there	لا يَسْكُنَنَّ هناك
We don’t go out at night	لا نَخْرُجَنْ في اللَيْل

• Following an oath:

By God I will study hard	وَاللّهِ لأَدْرُسَنَّ باجتهاد
By God I will punish the thief	تَاللّهِ لأُعاقِبَنْ السارِق

Note: When the emphatic nūn is used for an oath it’s usually combined with the emphatic lām.

• After a conditional particle combined with ما:

{And if you fear treachery from any people (with whom you have a covenant) then publicly throw their covenant at them…} Qurʾān [al-Anfāl : 58]	{…وَإِمَّا تَخَافَنَّ مِن قَوْمٍ خِيَانَةً فَانبِذْ إِلَيْهِمْ عَلَىٰ سَوَاءٍ}  القُرْآن [الأنفال: 58]
{And whether or not We take you away [in death], indeed, We will take retribution upon them} Qurʾān [al-Zukhruf : 41]	{فَإِمَّا نَذْهَبَنَّ بِكَ فَإِنَّا مِنْهُم مُّنتَقِمُونَ}  القُرْآن [الزخرف: 41]

Conjugation

• The heavy nūn (نُون التَوكِيد الثَقِيلة)

مُثَنّى (dual)	جمع (plural)	مُفْرَد (singular)	المُضارِع Imperfect
نَحْنُ نَفْعَلَنَّ		أنا أَفْعَلَنَّ	المُتَكَلِّم  1st person
أَنْتُما تَفْعَلانَّ	أَنْتُم تَفْعَلُنَّ	أنتَ تَفْعَلَنَّ	المُذَكَّر masc.	المُخاطَب  2nd person
	أَنْتُنَّ تَفْعَلْنَانَّ	أَنتِ تَفْعَلِنَّ	المُؤَنَّث fem.
هُما يَفْعَلانَّ	هُم يَفْعَلُنَّ	هُوَ يَفْعَلَنَّ	المُذَكَّر masc.	الغائِب  3rd person
هُما تَفْعَلانَّ	هُنَّ يَفْعَلْنانَّ	هِيَ تَفْعَلَنَّ	المُؤَنَّث fem.

مُثَنّى (dual)	جمع (plural)	مُفْرَد (singular)	الأَمْر Imperative
اِفْعَلانِّ	اِفْعَلُنَّ	اِفْعَلَنَّ	المُذَكَّر masc.	المُخاطَب  2nd person
	افْعَلْنَانِّ	اِفْعَلِنَّ	المُؤَنَّث fem.

• The light nūn (نُون التَوكِيد الخَفِيفة) 

مُثَنّى (dual)	جمع (plural)	مُفْرَد (singular)	المُضارِع Imperfect
نَحْنُ نَفْعَلَنْ		أنا أَفْعَلَنْ	المُتَكَلِّم  1st person
N/A	أَنْتُم تَفْعَلُنْ	أنتَ تَفْعَلَنْ	المُذَكَّر masc.	المُخاطَب  2nd person
	N/A	أَنتِ تَفْعَلِنْ	المُؤَنَّث fem.
N/A	هُم يَفْعَلُنْ	هُوَ يَفْعَلَنْ	المُذَكَّر masc.	الغائِب  3rd person
N/A	N/A	هِيَ تَفْعَلَنْ	المُؤَنَّث fem.

Note: The light nun doesn’t exist in dual and feminine plural forms

مُثَنّى (dual)	جمع (plural)	مُفْرَد (singular)	الأَمْر Imperative
N/A	اِفْعَلُنْ	اِفْعَلَنْ	المُذَكَّر masc.	المُخاطَب  2nd person
	N/A	اِفْعَلِنْ	المُؤَنَّث fem.

Emphatic lām / لام التَوكِيد

The particle لَـ called لام التَوْكِيد (= the emphatic lām), can precede a noun or a verb to give it more force. It can be used:

• at the beginning of a sentence with what is called the ‘starting lām’ (لام الاِبْتِداء): 

He is (indeed) the best driver	لَهُوَ أَفْضَلُ السُوَّاقِ
The sun is (indeed) shining	لَلشّمْسِ مُشْرِقة

• following an oath with the ‘lām of oath’ (لام القسم):

By God, I will study hard	وَاللّه لأَدْرُسَنَّ باجتهاد
By God I will punish the thief	تَاللّه لأُعاقِبَنْ السارِق