Firm
Firm adjective - Not showing weakness or uncertainty.
Proof and firm are semantically related in impervious topic. In some cases you can use "Proof" instead an adjective "Firm".
Proof
Proof adjective - (used in combination or as a suffix) able to withstand.
Firm and proof are semantically related in characteristic topic. Sometimes you can use "Firm" instead an adjective "Proof", if it concerns topics such as impervious.
Mutual synonyms
How words are described
| best | best firm | best proof |
| original | original firm | original proof |
| legitimate | legitimate firm | legitimate proof |
| legal | legal firm | legal proof |
| Other adjectives: main, important, supernatural, new, official. | ||
Both words in one sentence
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As proof, he cites a vastly inferior evil organization pulling in many important jobs simply because they had a top-rate design firm redesign their secret base.
Source: Supervillain Lair -
He's living proof that being a flaming queen stereotype will NOT do anything to stop you from having Crowning Moments Of Awesome, especially considering he's a firm follower of the show philosophy of doing the impossible.
Source: Camp Gay -
Ellie Arroway spends the first quarter of the film demonstrating firm belief in the existence of alien life, even at the detriment of her career, despite the fact there is no empirical proof, the exact thing she stated as the reason she doesn't believe in a god.
Source: Film / Contact
Cite this Source
Proof and Firm. (2016). Retrieved 2026, August 15, from https://thesaurus.plus/related/firm/proof
Firm & Proof. N.p., 2016. Web. 15 Aug. 2026. <https://thesaurus.plus/related/firm/proof>.
Proof or Firm. 2016. Accessed August 15, 2026. https://thesaurus.plus/related/firm/proof.
Google Ngram Viewer shows how "firm" and "proof" have occurred on timeline