Complex sentence: The Parliament of the United Kingdom of Great Britain and Northern Ireland, commonly known as the British Parliament is the leglislative body of the United Kingdom, and, when combined with the Crown, forms the supreme unchallengeable legislative authority over the United Kingdom and its territories.
Split into simpler sentences: The Parliament of the United Kingdom of Great Britain and Northern Ireland, commonly known as the British Parliament, is the leglislative body of the United Kingdom. When combined with the Crown, forms the supreme unchallengeable legislative authority over the United Kingdom and its territories.