The letter "ا" is the first letter of the Arabic alphabet, known as "alif." It is a vowel and can represent a long "a" sound. In Arabic script, "ا" is written in a straight vertical line and does not connect to the letters that follow it. In terms of pronunciation, "ا" is pronounced as "a" in words like أب (father) and أم (mother). It plays a crucial role in forming words and can also appear in different forms depending on its position in a word, such as at the beginning, middle, or end.