primary(that which is placed ahead of others) adjective [UK: ˈpraɪ.mə.ri] [US: ˈpraɪ.ˌme.ri]I attend primary school. = Frequento la scuola primaria.
prime(first in importance, degree, or rank) adjective [UK: praɪm] [US: ˈpraɪm]That's a matter of prime importance. = Quello è un problema di primaria importanza.