voucher vs meal ticket

voucher and meal ticket both are nouns.

Word	Noun	Adjective	Verb	Adverb
voucher	Yes	No	No	No
meal ticket	Yes	No	No	No

As nouns, meal ticket is a hyponym of voucher; that is, meal ticket is a word with a more specific, narrower meaning than voucher:

voucher: a negotiable certificate that can be detached and redeemed as needed
meal ticket: coupon redeemable at a restaurant and entitling the holder to a meal

Other hyponyms of voucher include book token, luncheon voucher, twofer.

voucher (noun)	meal ticket (noun)
a negotiable certificate that can be detached and redeemed as needed	coupon redeemable at a restaurant and entitling the holder to a meal
a document that serves as evidence of some expenditure	a source of income or livelihood
someone who vouches for another or for the correctness of a statement