The Texas Triangle is one of eleven megaregions in the United States. These are urban areas that are much greater in scale than a metropolitan statistical area (MSA), defined by the US Census Bureau. These regions also are known as megapolitan areas. This term is derived from the fact that the three main cities in the Texas Triangle are connected by a highway system of Interstate 45, Interstate 10, and Interstate 35, which form a triangle when connected. The area is sometime also referred to as the Texaplex.