Are the development phases vision,definition ,development and maintenance same

Are the development phases vision,definition ,development and maintenance same as requirement levels. are two diferent things.

Vision, Definition, Development and Maintenance are the four phases of software development. During the vision phase, we capture the high level business requirement of the system and we try to find out as why we need to develop the software and what objective we want to achieve by using this software. In definition phase, we try to find out the different activities which will be involved in order to achieve the business objective. During this phase, we capture different type of requirements satisfied by the proposed software. Different requirement documents are written in this phase. So, requirement gathering process is completed during this phase. After once this phase is completed, only then the actual development of the software starts.