this is Hamza , it is not on of 28 Arabic letters , it is a glottal stop means that it is not pronounced with tongue or lip , just to level of glottis. so it an mostly added to ALif to be alif long plus hamza and here we call it hamzt qata`a a`a=ain some time with alya almaqsora ئ like Azrael عزرائيل or at the end of word like enshaa انشاء means estiblishment and also has some other meanings. this link can do help http://en.wikipedia.org/wiki/Hamza good luck

this is a letter, you pronounced it like أ but used just in last of the word

It is used at the end of many words. It is pronounced like أ

It's a letter is called "همزة - Hamza". It can come in the start of the word, the middle or even at the end. It's used with the letters "الف - Alef" ,"واو - Waw" or " ياء -Ya' " and it also comes alone. With Alef : أخبار News إغلاق Closing انشأ Established مأساة Tragedy With Waw: مؤامرة plot تواطؤ Collusion With Ya' : ينشئ Establish رئيس Leader Alone on the line: سماء Sky مروءة Generosity

it is called همزه it is a letter like example that people wrote up سماء سوداء