A sultan is an Islamic monarch. Sultan is usually used by monarchs of Arabic, Turkish or Malaysian ethnicity as opposed to Khan or Shah. In modern English, the term is gradually being replaced by king. The sultan's domain is properly called a sultanate. The feminine form is sultana.
... (died 1570), discovered the Hudson River and sailed up it to Albany, discovered Hudson Bay
Alexander von Humboldt, (1769-1859), explored Central and South America, ...