1
: very much : a lot
It's substantially [=considerably] less expensive to buy a used car than a new car.
A new car costs substantially more than a used car.
Costs have increased substantially [=significantly] in recent years.
2
a
: in a general or basic way
The methods are substantially [=essentially] the same.
b
: almost completely : mostly
There are still a few details to wrap up, but the project is substantially complete.
Cite this Entry
“Substantially.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/substantially. Accessed 20 Jun. 2026.
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