Instructions: Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.
Input: Sentence1: navigation requires knowing direction. 
Sentence2: Direction is designated first in reference to North or South, then to East or West.
Output:
direction