Wordlist utilities - merge wordlists
The word-list merging tool is used when you need to combine two or more wordlists in one.
If the 'Sort output wordlist' option is not set, merging comes down to simply adding new words, without sorting or checking for duplicates. In practice, however, more common is merging with sorting; it ensures that all the words in the output wordlist are alphabetically sorted and duplicate-free.
Sorting may take a considerable amount of memory; therefore, it is appropriate to set a limit for the amount of memory that can be used by the process (at the expense of a little downgrade of the operation speed).