The definite article of Arabic is الـ (Alif-Laam), known as لام التارف (Laam Al-tarif).
The first letter of the laam al-tarif is a Hamzat-Wasl (همزة وصل), an alif with a Saad (ص) written above it (ٱ). We do not write the ص on the alif in writing (we simply know it is there, as no words in Arabic begin with Alif (only Alif with Hamza (أ)). A Hamzat-Wasl takes the sound of a vowel immediately before it, if there is one. If not, it makes the same sounds a fatha at the beginning of the word (أَ).
An example of the hamzat-wasl taking the sound of a preceding vowel is الأُممُ الـمُتَّحِدة) (Al-Umamu ul-Muttahida), "The United Nations."
The spelling of laam al taareef,is with ain,and not alif. لام التعريف ،here it means the. But in some places it means 'all'.then it is known as laam aljins. Where jins,means the whole category. E.g.alhamdu=all praise الحمد