To identify the word related to "gregariousness," I would need to see the specific passage you're referencing. However, if you are looking for the part of speech related to "gregariousness," the word you're looking for is likely "gregarious," which is an adjective.
If you provide the passage, I can give you a more precise answer. Without the passage, I suggest that you look for "gregarious" or any variation of it to determine its part of speech.