Answer:
noun
Step-by-step explanation:
A dictionary gives the definition of a word, but also its use/functions (like noun, verb, adjective, and so on).
'n' stands for 'noun', to save space. It doesn't save much into a single entry (usually found once or twice)... but if you multiply that by 60 000 or 80 000 words in the dictionary, that sums up to a large number of characters saved... which translate into pages.