tax break vs tax deduction

tax break and tax deduction both are nouns.

Word	Noun	Adjective	Verb	Adverb
tax break	Yes	No	No	No
tax deduction	Yes	No	No	No

As nouns, tax deduction is a hypernym of tax break; that is, tax deduction is a word with a broader meaning than tax break:

tax break: a tax deduction that is granted in order to encourage a particular type of commercial activity
tax deduction: a reduction in the gross amount on which a tax is calculated; reduces taxes by the percentage fixed for the taxpayer's income bracket

Other hypernyms of tax break include deduction, tax write-off.

tax break (noun)	tax deduction (noun)
a tax deduction that is granted in order to encourage a particular type of commercial activity	a reduction in the gross amount on which a tax is calculated; reduces taxes by the percentage fixed for the taxpayer's income bracket