pitcher vs vessel

pitcher and vessel both are nouns.

Word	Noun	Adjective	Verb	Adverb
pitcher	Yes	No	No	No
vessel	Yes	No	No	No

As nouns, vessel is a hypernym of pitcher; that is, vessel is a word with a broader meaning than pitcher:

pitcher (noun)	vessel (noun)
the position on a baseball team of the player who throws the ball for a batter to try to hit	a craft designed for water transportation
an open vessel with a handle and a spout for pouring	an object used as a container (especially for liquids)
(baseball) the person who does the pitching	a tube in which a body fluid circulates
(botany) a leaf that is modified in such a way as to resemble a pitcher or ewer
the quantity contained in a pitcher