There are many ways in which you can increase your vocabulary as against memorising it. Rome was not built in one day. You can go to Google and in the search box type "word of the day". This will give you a link to many dictionaries that chooses a word of the day with explanation. Now, you must construct at least 5 sentences using that word.Only by constructing sentences will you be able to retain the meaning.
Another way is to play word games like a simple crossword puzzles.