The only one of its kind
Encoding Strategies:
linguistic

unique
unique
+
-o
adjective suffix
Único means unique and is a direct cognate of the English word.
único
unique, one of a kind
One of a kind, with nothing else quite like it.
Cada copo de nieve es únicoEvery snowflake is unique
Su estilo es completamente únicoHer style is completely unique
only, sole (sole)
If something is the one and only of its kind, then it's the sole one there is.
Fue el único que vino a la reuniónHe was the only one who came to the meeting
Es mi única oportunidadIt's my only chance