Writing is a medium of communication that represents language through the inscription of signs and symbols. In most languages, writing is a complement to speech or spoken language. Writing is not a language but a form of technology. Within a language system, writing relies on many of the same structures as speech, such as vocabulary, grammar and semantics, with the added dependency of a system of signs or symbols, usually in the form of a formal alphabet. The result of writing is generally called text, and the recipient of text is called a reader. Motivations for writing include publication, storytelling, correspondence and diary. Writing has been instrumental in keeping history, dissemination of knowledge through the media and the formation of legal systems. As human societies emerged, the development of writing was driven by pragmatic exigencies such as exchanging information, maintaining financial accounts, codifying laws and recording history. Around the 4th millennium BCE, the complexity of trade and administration in Mesopotamia outgrew human memory, and writing became a more dependable method of recording and presenting transactions in a permanent form. In both Ancient Egypt and Mesoamerica writing may have evolved through calendrics and a political necessity for recording historical and environmental events.