On sufferance is an idiomatic expression that means doing something only because the person in authority allows it. You can use synonyms to convey the same meaning, like "with reservation," "tolerated," "with a nod," "with leave," and "acceptable for now." Other synonyms for on sufferance include "unwelcome," "uninvited," and "unapproved." These words suggest that the person or situation is reluctantly tolerated by someone in charge. In contrast, "with permission," "authorized," and "officially allowed" imply overt approval. Using synonyms allows you to vary your language and keep your writing more engaging. Whether you use on sufferance or its alternatives, make sure you consider the context and tone you're aiming for.