pledge vs vow

pledge and vow both are nouns.

Word	Noun	Adjective	Verb	Adverb
pledge	Yes	No	Yes	No
vow	Yes	No	Yes	No

As nouns, vow is a hyponym of pledge; that is, vow is a word with a more specific, narrower meaning than pledge:

pledge: a binding commitment to do or give or refrain from something
vow: a solemn pledge (to oneself or to another or to a deity) to do something or to behave in a certain manner

Other hyponyms of pledge include guarantee, warrant, warrantee, warranty, guarantee, plight, troth.

As verbs, vow is a hyponym of pledge; that is, vow is a word with a more specific, narrower meaning than pledge:

Other hyponyms of pledge include guarantee, vouch, covenant, covenant.

pledge (noun)	vow (noun)
a binding commitment to do or give or refrain from something	a solemn pledge (to oneself or to another or to a deity) to do something or to behave in a certain manner
a drink in honor of or to the health of a person or event
someone accepted for membership but not yet fully admitted to the group
a deposit of personal property as security for a debt

pledge (verb)	vow (verb)
promise solemnly and formally	make a vow; promise
bind or secure by a pledge	dedicate to a deity by a vow
give as a guarantee
propose a toast to
pay (an amount of money) as a contribution to a charity or service, especially at regular intervals