Malacopterygian is a term used to describe fish species that have soft and flexible fins. There are several synonyms for this term, including soft-rayed fish, soft-finned fish, and soft-fin fishes. Other synonyms include teleosts, which refers to all modern bony fish, or Acanthopterygii, which is a larger group that includes species with both hard and soft fins. Malacopterygian species are found in both freshwater and saltwater habitats and play important ecological roles in aquatic ecosystems. Synonyms for this word help to expand our understanding of the diverse range of fish species that inhabit our planet.