Think of a Dictionary as an Array with 2 values per entry, that are associated with each other. That's why in programming terms it's called an 'associative array'. Each entry has a 'key' (text) and a 'value' (number).
Anyway, I did some testing and created an Array of 33,000 words and found that a seach for even the last word is pretty much instantaneous using the "ContainsValue" condition of the Array.