bellwether vs leader

bellwether and leader both are nouns.

Word	Noun	Adjective	Verb	Adverb
bellwether	Yes	No	No	No
leader	Yes	No	No	No

As nouns, leader is a hypernym of bellwether; that is, leader is a word with a broader meaning than bellwether:

bellwether (noun)	leader (noun)
sheep that leads the herd often wearing a bell	a featured article of merchandise sold at a loss in order to draw customers
someone who assumes leadership of a movement or activity	a person who rules or guides or inspires others