Partly because the language is already so rich, the "marginal utility" of new words is declining: Existing things are already well described.
WSJ: Culturomics Looks at the Birth and Death of Words
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。