Complex sentence: The Sisterhood Is Global Institute (SIGI), an international nonprofit NGO with consultative status to the United Nations, has for almost three decades functioned as the world's first feminist think-tank.
Split into simpler sentences: The Sisterhood Is Global Institute (SIGI) is an international nonprofit non-governmental organization with consultative status to the United Nations. For almost three decades, it has functioned as the world's first feminist think-tank.