a male adult human who is free and intelligent, to whom Allah has revealed a Sacred Law be it in book form or otherwise, and who was ordered by Him to convey it to the servants
a female cannot become a messenger
A Nabi (Prophet) is:
a male adult human who is free and intelligent, to whom Allah has revealed a Sacred Law, even though He did not order him to convey it to the creation
all Rasuls are Nabis
not all Nabis are Rasuls
a female cannot become a prophet
Mandatory attributes of rasuls:
siddiq (truthful). Always speaks the truth.
amanah (trustworthy). Never betrays anybody.
tabligh (conveying). Conveys all that Allah asked to convey.
fathanah (wise). Have wisdom when dealing with their people.