to a total exceeding the half million words listed in unabridged dictionaries.是介词短语
to 是介词
a total是介词宾语 后面是现在分词短语 作定语 修饰 a total
exceeding是现在分词
the half million words是 现在分词的宾语 后面是过去分词短语 修饰 words
listed 是过去分词
in unabridged dictionaries是 介词短语 作过去分词 listed的状语