The word "unpermanent" implies something that is not permanent, but there are several synonyms that could be used instead. "Temporary," "transient," "ephemeral," "fleeting," and "brief" are all synonyms that convey the same idea. "Impermanent," "mutable," and "unstable" are other words that could be used as well. In each case, the idea is the same: something that is not permanent and may not endure over time. The choice of word may depend on the context in which it is being used, as well as the speaker's intent and the audience's understanding.