sirenita
little mermaid
siren
mythical creature
+
-ita
little (diminutive)
Sirenita means little mermaid and can be thought of as siren0 (mythical creature0) + -ita1 (little1), so it's a little mermaid or siren.
noun
- little mermaidLittle mermaidMi hija quiere disfrazarse de sirenita para Halloween. // My daughter wants to dress up as a little mermaid for Halloween.