(1) اَلْكِتَاب the book

(2) اَلْغُرْفَة the room

(3) اَلْقَلَم the pen

(4) اَلْبَيْت the house

In the is list, the words are definite nouns since they start with the definite article اَلْ. We must pronounce the alif of اَلْ because if we drop it, the remainder words لْكِتَاب, لْغُرْفَة, لْقَلَم, and لْبَيْت become difficult to pronounce. So, the function of connective alif is to ease the pronunciation of the words. 

(1) اُكْتُبْ! write

(2) اِجْلِسْ! sit down

(3) اِنْهَضْ! stand up

(4) اُنْظُرْ! look

Here, the words are imperative verbs. So, they start with alif al-wasl. As the letters that follow alif al-wasl have a sukuun over them, we must pronounce it. In other words, the pronunciation of كْتُبْ, جْلِسْ, نْهَضْ, and نْظُرْ is difficult the connective alif.

(1) اِنْكَسَرَ it broke

(2) اِبْتَسَمَ he smiled

(3) اِسْتَخْدَمَ he used

(4) اِسْتَمْتَعَ he had fun

These words are past tense verbs. Composed of five or six letters, they always begin with alif al-wasl which we must pronounce. If we drop it, the remainder words become difficult to pronounce because they start with a letter that is saakin.

(1) اِنْكِسَار breakage

(2) اِبْتِسَام smiling

(3) اِسْتِخْدَام usage

(4) اِسْتِمْتَاع having fun

Derived from the past tense verbs above, these words are verbal nouns. Like the verb roots, they always begin with alif al-wasl. When they occur alone or at the beginning of a sentence, alif al-wasl must be pronounced. 

The Rule: alif al-wasl in isolated words must be pronounced because it is difficult in Arabic to pronounce a word that begins with a letter that has a sukuun over it.

(1) إِلَىْ الْيَمَن to Yemen ⇐ إِلَلْيَمَن

(2) مِنَ الْيَمَن from Yemen ⇐ مِنَلْيَمَن 

(3) عَنِ الْيَمَن about Yemen ⇐ عَنِلْيَمَن

(4) عَلَىْ الْيَمَن against Yemen ⇐ عَلَلْيَمَن 

(5) حَتَّىْ الْيَمَن even Yemen ⇐ حَتَّلْيَمَن

(6) فِيْ الْيَمَن in Yemen ⇐ فِلْيَمَن

The word اَلْيَمَن begins with alif al-wasl. It is preceded by another word—a preposition. When reading the whole phrase, alif al-wasl is not pronounced. With إِلَى, عَلَى, حتَّى, and فِي, the ى and ي is dropped in speech, and the لْ of الْيَمَن is joined to the preceding letter. With عَنْ and مَنْ, the sukuun over the نْ is replaced by fatha نَ or kasra نِ because of the juxtaposition of two sukuuns, نْ and لْ.

(1) وَاُكْتُبْ! and write ⇐ وَكْتُبْ

(2) وَاِجْلِسْ! and sit down ⇐ وَجْلِسْ

(3) وَاِنْهَضْ! and stand up ⇐ وَنْهَضْ

These imperative verbs are preceded by the connecting word وَ. This word forces alif al-wasl of the imperative verbs to drop when we speak. So, our speech sounds more natural.

(1) فَاِنْكَسَرَ so/then it broke ⇐ فَنْكَسَرَ

(2) فَاِبْتَسَمَ so/then he smiled ⇐ فَبْتَسَمَ

(3) فَاِسْتَخْدَمَ so/then he used ⇐ فَسْتَخْدَمَ

(4) فَاِسْتَمْتَعَ so/then he had fun ⇐ فَسْتَمْتَعَ

Here, the past form verbs are preceded by the connecting particle فَـ 'so/then'. This particle forces alif al-wasl of the verbs to drop when we speak. Therefore, our speech becomes natural and connected.

(1) بِاِنْكِسَارِ by breakage of ⇐ بِنْكِسَارِ

(2) لِـاِبْتِسَامِ for smiling ⇐ لِبْتِسَامِ

(3) كَاِسْتِخْدَامِ  as usage of ⇐ كَسْتِخْدَامِ

(4) لِـاِسْتِمْتَاعِ for enjoying ⇐ لِسْتِمْتَاعِ 

In this list, the verbal nouns are preceded by the prepositions بِـ 'by', لِـ 'for', and كَـ 'as'. They trigger the dropping of alif al-wasl when we speak.  As a result, our speech becomes more connected. بِنْكِسَارِ is certainly a lot more natural than بِاِنْكِسَارِ as a spoken form.

The Rule: When a preposition or a connecting particle precedes a word that begins with alif al-wasl, it forces alif al-wasl to drop in the spoken form of Arabic. So, alif al-wasl in such cases is not pronounced. However, it must be kept in writing.

(1) كِتَابُ الْوَلَدِ the boy’s book ⇐ كِتَابُلْوَلَدِ

(2) غُرْفَةُ الْجُلُوسِ the sitting room ⇐ غُرْفَتُلْجُلُوسِ

(3) بَيْتُ الْكَلْبِ the dog’s house ⇐ بَيْتُلْكَلْبِ

(4) حَارِسُ الْمَرْمَى the goal keeper ⇐ حَارِسُلْمَرْمَى

Looking at the first word in each of these phrases, it is assigned the nominative case mark (i.e., the dhamma) over the last letter. The second word begins with alif al-wasl. The dhamma forces alif al-wasl to drop in connected speech. So, our spoken form of Arabic becomes natural.

(1) كِتَابَ الْوَلَدِ the boy’s book ⇐ كِتَابَلْوَلَدِ

(2) غُرْفُةَ الْجُلُوْسِ the sitting room ⇐ غُرْفَتَلْجُلُوسِ

(3) بَيْتَ الْكَلْبِ the dog’s house ⇐ بَيْتَلْكَلْبِ

(4) حَارِسَ الْمَرْمَى the goal keeper ⇐ حَارِسَلْمَرْمَى

Here, the first word in each of these phrases is assigned the accusative case mark (i.e., the fatha) over the last letter. The second word begins with alif al-wasl. So, the fatha forces alif al-wasl to drop in connected speech. Hence, our speech sounds more natural. 

(1) كِتَابِ الْوَلَدِ the boy’s book ⇐ كِتَابِلْوَلَدِ

(2) غُرْفُةِ الْجُلُوْسِ the sitting room ⇐ غُرْفَتِلْجُلُوسِ

(3) بَيْتِ الْكَلْبِ the dog’s house ⇐ بَيْتِلْكَلْبِ

Unlike the above two lists, the first word in each of these phrases is assigned the genitive case mark (i.e., the kasra) over the last letter. The second word begins with alif al-wasl. Therefore, the kasra forces alif al-wasl to drop in connected speech. 

The Rule: When a noun that starts with the definite article الْـ is preceded by a word (a noun in the above examples) that is assigned the case mark (i.e. fatha, dhamma, or kasra), the alif of الْـ becomes silent. 

(1) لِـ + اَلْوَلَدِ = لِلْوَلَدِ for the boy

(2) لِـ + اَلْوَطَنِ = لِلْوَطَنِ for the country

(3) لِـ + اَلْمُدِيرِ = لِلْمُدِيرِ for the boss

When alif al-wasl of the definite article الْـ is preceded by the preposition لِـ, which means for, it is neither written nor pronounced.

The Rule: when the لِـ, which is mostly used to talk about ownership or possession, precedes a definite noun (i.e., a noun that begins with the definite article الْـ), alif al-wasl of الْـ is omitted in writing. 

(1) اَلشَّمْس the sun

(2) اَلسِّكِّين the knife

(3) اَلطَّالِب the student

(4) كَالشَّمْسِ like the sun ⇐ كَشَّمْسِ

(5) بِالسِّكِينِ with the knife ⇐ بِسِّكِّينِ

(6) فَالطَّالِبِ so the student ⇐ فَطَّالِبِ

When the definite article الْ precedes a noun that starts with a sun letter, the لْ gets assimilated to the sun letter. And the sun letter, in turn, becomes a geminate (i.e. doubled): شْشَ ⇐ شَّـ ، سْسِ ⇐ سِّـ ، طْطَ ⇐ طَّـ. 

In كَالشَّمْسِ , بِالسِّكِّينِ, and فَالطَّالِبِ, alif al-wasl is dropped and the ل is assimilated to the following sun letter.

(1) نَظَّارَةَ الطَّبِيْبِ the doctor’s glasses ⇐ نَظَّارَتَطَّبِيبِ

(2) يَوْمُ الثُّلَثَاءِ Tuesday ⇐ يَوْمُثُّلَثَاءِ

(3) سَيَّارَةِ الرَّجُلِ the man’s car ⇐ سَيَّارَتِرَّجُلِ 

The case mark assigned to the last letter of the first word in these phrases forces alif al-wasl to drop and the لْ to assimilate to the following sun letter, which becomes doubled.