Something may be described as tantamount to something else if it is equal in value, meaning, or effect.

// The pop star’s fans see any criticism of her music as tantamount to a crime.

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“... conducting requires more than merely gesturing with a baton—some pieces of music are tantamount to 80 minutes of hard cardio ...” — Mark Shanahan, The Boston Globe, 15 Mar. 2026

Although tantamount (from the Anglo-French phrase tant amunter, meaning “to amount to as much”) was used three different ways in the early 17th century—as a noun, verb, and adjective—the adjective form has since proven paramount to English users: it’s still in use while the noun and verb are obsolete. This is not to say that the adjective hasn’t experienced change over the years. While it was once acceptable to use tantamount in a variety of different sentence structures, nowadays it is almost always followed by the word to. And to use it before a noun, as in “the two old friends exchanged tantamount greetings,” would now be considered, er, tantamount to riding a penny-farthing or boneshaker onto the expressway.