Heavy
Heavy adjective - Having great weight.
Usage example: this trunk full of books is much too heavy for one person to lift
Substantial is a synonym for heavy in solid topic. In some cases you can use "Substantial" instead an adjective "Heavy", when it comes to topics like considerable, big, weighty, sizeable.
Substantial
Substantial adjective - Having great meaning or lasting effect.
Usage example: substantial changes to the school dress code that made a lot of people unhappy
Heavy is a synonym for substantial in characteristic topic. Sometimes you can use "Heavy" instead an adjective "Substantial", if it concerns topics such as big, important.
Mutual synonyms
Both words in one sentence
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Most weapons in Outpost 2 are relatively slow firing (about one shot per second if you're lucky) and don't get any substantial upgrades to their rate of fire, so the Tiger heavy tank compensates this by mounting two of whatever weapon it's given.
Source: Beam Spam -
In Jambier's basement storehouse, Grandgil finds out the load of pork he and Marcel have to smuggle throughout Paris is quite heavy and thus demands a substantial increase of his salary to Jambier, who refuses categorically.
Source: Film / The Trip Across Paris -
While the North Vietnamese were able to capture and retain a substantial chunk of South Vietnamese territory, they suffered very heavy losses, including most of their armor and artillery, under weight of U.S.
Source: Useful Notes / The Vietnam War
Cite this Source
Substantial and Heavy. (2016). Retrieved 2026, August 15, from https://thesaurus.plus/related/heavy/substantial
Heavy & Substantial. N.p., 2016. Web. 15 Aug. 2026. <https://thesaurus.plus/related/heavy/substantial>.
Substantial or Heavy. 2016. Accessed August 15, 2026. https://thesaurus.plus/related/heavy/substantial.
Google Ngram Viewer shows how "heavy" and "substantial" have occurred on timeline