The English word pasta generally means noodles and other food products made from a flour and water paste, often including also egg and salt. The word comes from Italian pasta which means basically "paste". Cooking is the process of preparing food by applying heat, selecting, measuring and combining of ingredients in an ordered procedure for producing safe and edible food. The process encompasses a vast range of methods, tools and combinations of ingredients to alter the flavor, appearance, texture, or digestibility of food. Factors affecting the final outcome include the variability of ingredients, ambient conditions, tools, and the skill of the individual doing the actual cooking. The diversity of cooking worldwide is a reflection of the aesthetic, agricultural, economic, cultural, social and religious diversity throughout the nations, races, creeds and tribes across the globe. Applying heat to a food usually, though not always, chemically transforms it, thus changing its flavor, texture, consistency, appearance, and nutritional properties. Methods of cooking that involve the boiling of liquid in a receptacle have been practised at least since the 10th millennium BC, with the introduction of pottery.