There would be about 42 words in such a dictionary, from 6-letter to 2-letter words. If 1-letter words are allowed, then we need to add O and I, perhaps. The word I has at least three meanings: first person pronoun; Roman numeral for 1; representation for square root of minus 1. O can represent an exclamation; a respectful address ("O Lord"); chemical symbol for oxygen. "Potion" and "option" are anagrams. The 3-letter words have the largest set (about 18). The 1-letter and 6-letter words have the smallest set (2). Therefore, OPTION shares the lowest rank (6) in terms of numbers in the set, but shares the highest (1) in terms of the most letters used (maximum).
Alphabetically it comes about position 19.