Being a member of a group or organization is a common thing in our social lives. However, constantly using the same phrase "be a member of" can make your writing or speech repetitive. Thankfully, there are many synonyms to replace it with. You can use expressions like "belong to," "take part in," "join," "enroll in," "be a part of," "affiliate with," "associate with," or "subscribe to." These synonyms can add variety to your language and make your writing more engaging. Remember to choose the right synonym depending on the context of your sentence and the level of formality you want to convey.