Fifteenths have a number of different synonyms, depending on the context in which the word is used. In some cases, "fifteenth" can be substituted, as it has the same basic meaning of one part out of 15. Other potential synonyms include "one-fifteenth," "1/15th," or "15 percent." In legal or musical contexts, terms like "quotient" or "crotchet" may also be used to describe the concept of dividing something into 15 equal parts. Ultimately, the choice of synonym will depend on the specific use case and the writer or speaker's preference for one particular term over another.