There are several synonyms for the phrase "here till Sunday," which refers to someone's duration of stay until the end of the week. Some appropriate synonyms include "until the weekend," "until Sunday comes," "lasts until Sunday," or simply saying "staying until Sunday." These phrases imply that the person will remain in their current location until the end of the week and provide an indication for their availability over the weekend. It is essential to communicate effectively with others if you plan to stay in a specific location until Sunday to ensure that all parties involved understand the intended time frame.