an Englishman, two Englishmen (英国人,英国男人)
an Englishwoman, two Englishwomen (英国女人)
a Frenchman, two Frenchmen (法国人,法国男人)
a Frenchwoman, two Frenchwomen (法国女人)
He/She is English / French. (English / French是形容词)
He is an English boy. She is an English girl.
He is a French boy. She is a French girl.
不能说 “He/She is an English.”以及“He/She is a French.”