The differences between a hijab and an abaya are considerable, as they are two very different garments. A hijab is a headscarf or head covering worn by women in observance of Islamic modesty standards. An abaya is a long robe or cloak that covers a woman's body and is typically worn over other clothing. In some cases, a woman will wear a hijab and an abaya together, although some Muslim women or women living in Islamic countries may decide to wear only a hijab. The abaya is typically worn in the Gulf states, such as Saudi Arabia, while women in other predominately Muslim countries may wear a different type of overgarment or not wear one at all.
Modest dress requirements have sparked some controversy among Muslims, and there are different interpretations of how covered a woman should be when appearing in public or in the presence of men other than her husband or close relatives. Typically, however, women are expected to cover their head and hair, to cover their bodies entirely except for their hands and face, and to wear clothing that conceals the shape of their bodies. Covering the head and hair is typically accomplished by wearing a hijab, which may cover not only a woman's hair but also her shoulders, chest, and in some cases much of her back and torso.
While some women fulfill the other requirements by simply wearing clothing that fits loosely and that completely covers the arms and legs, some women will wear a garment over these clothes for additional coverage. In Iran, women may wear a loose raincoat, called a manteau or a chador, which is a large piece of fabric draped over the head and body. Women in other countries may wear a jilbab, which is a long coat-dress that often buttons down the front, or the abaya.
Abaya styles vary, and some include a hood, while others provide no head covering at all. In either case, a woman who is concerned about coverage will wear the hijab and an abaya at the same time, as a hooded abaya doesn't provide the degree of head and hair coverage that a hijab does. In addition to a hijab and an abaya, some women may also wear a niqab, a veil that covers most or all of the face. Other accessories used to provide additional coverage are arm gauntlets, which cover a woman's arms when she wears an abaya with loose sleeves, and gloves, which cover her hands.