"Sustainable development is development that continues to meet requirements without compromising the ability of future generations to live a quality life." Sustainable development is commonly believed to have three components: environment, society and economy. According to the toolkit the three should be considered as overlapping and congruent circles. In this case, the area of ​​overlap, or center, is considered human well-being. Further alignment of said circles would indefinitely lead to the increase of the center, human well-being. The balance of each component delicately depends on the next. For example, a healthy and prosperous society relies on a healthy environment to provide food and resources, safe drinking water, and clean air to its citizens. The sustainability model denies the argument that casualties in environmental and social jurisdictions are inevitable. Added to this is the argument that casualties are acceptable consequences of economic development. Therefore, the authors consider sustainability as a paradigm for thinking about a future in which environmental, social and economic considerations are balanced in the pursuit of development and improved quality of life. The lower middle class is a subdivision of the larger middle class. class. Taken together the term refers to the group of middle-class families or individuals who have not achieved the upper-middle-class status associated with the prestige ranks of the middle class. The lower middle class makes up about a third of families, composed mainly of semi-professionals, such as lower-level managers or school teachers, small business owners, and skilled craftsmen. The lower middle class is shit... half paper... who continues to meet the requirements without compromising the ability of future generations to live a quality life. Sustainable development is commonly believed to have three components: environment, society and economy. Sustainability is considered an archetype for thinking about a future in which environmental, social and economic considerations are stable in the pursuit of expansion and improvement of the quality of life. Works Cited International Journal of Sustainability in Higher Education> Volume 4 issue 1. (2000).http://www.emeraldinsight.com/journals.htm?articleid=839800&show=abstractEducation for Development Toolkit> Version 2 (2002).http: //www.esdtoolkit.org/discussion/whatisesd.htmInsight-University of Gloucestershire > Sustainability Education (2005-2010).http://insight.glos.ac.uk/sustainability/Education/Pages/default.aspx