the male ruler of an empire
"The emperor declared war on his rival kingdoms to expand the empire's borders."
red table grape of California
"The farmer harvested tons of crisp Emperor grapes from his vineyard in Napa Valley."
large moth of temperate forests of Eurasia having heavily scaled transparent wings
"The emperor, a large moth found in the temperate forests of Eurasia, was spotted fluttering through the woods with its heavily scaled transparent wings catching the sunlight."
large richly colored butterfly
"The emperor butterfly danced gracefully among the tall grasses, its vibrant blue wings catching the sunlight."
The male monarch or ruler of an empire.
"The emperor ruled over a vast empire that stretched from Europe to Asia."
In plain English: An emperor is a male ruler who has power over an entire empire, which includes many different countries and people.
"The emperor sat on his throne to address the people gathered in the palace square."
The title of an emperor.
"The inscription on his tombstone clearly bore the imperial title of Emperor."
The word "emperor" comes from the Latin imperātorem, which means "commander." It entered English through Anglo-Norman and Middle English, originally referring to someone who holds supreme command.