mindmap root((延长)) extend implies a drawing out of extent in space or time and may also imply increase in width, scope, area, influence, or range: ~ welfare services. 这里用extent解释extend，属于自释 extent是所有范围的基础词，对range的解释是range is the general term indicating the extent，即range泛指extent lengthen suggests an increase of length in either time or space: ~ the school year. elongate usually implies increase in spatial length and frequently suggests stretching: the dancer's ability to ~ her body. prolong suggests chiefly increase in duration especially beyond usual, normal, or pleasing limits: ~ed illness. protract adds to prolong implications of needlessness, vexation, or indefiniteness: ~ed litigation.