a prolonged fantasy world invented by children; can have a definite geography and language and history
paracosm:
From Ancient Greek παρ? ?(pará, “beside, alongside”) + κ?σμο? ?(kósmos, “world, universe”).
英汉双解词典包含3185865条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。