The letter "Y" is one of the least commonly used letters in the English language, and therefore, it doesn't have a lot of synonyms. However, there are a few words that can be used in place of "Y" in certain contexts. For example, the word "and" can be used in place of "Y" in casual conversation or informal writing. In more formal writing, the word "conjointly" can be used as a synonym for "Y". Additionally, the word "together" can be used as an alternative in some cases. Overall, while there may not be many synonyms for "Y", there are still a few options available to writers and speakers who want to switch things up.