fusion [fusions](act of melting something by heating it) noun [UK: ˈfjuːʒ.n̩] [US: ˈfjuːʒ.n̩]
melting(process of changing the state of a substance) noun [UK: ˈmelt.ɪŋ] [US: ˈmelt.ɪŋ]Melting polar icecaps could also contribute to an increase in sea levels. = El derretimiento de los casquetes polares también podría contribuir al aumento del nivel del mar.
thaw [thaws](the melting of ice, snow or other congealed matter) noun [UK: θɔː] [US: ˈθɒ]