Significant vs Substantial

When to use each in English, with meaning, register, and examples.

Significant

Top 1,000 (very common) B2 adjective

Substantial

Top 2,000 (common) C1 adjective

Most common: Significant

	Significant	Substantial
Pronunciation	🇬🇧 /["/sɪɡˈnɪfɪkənt/"]/ 🇺🇸 /["/sɪɡˈnɪfɪkənt/"]/	🇬🇧 /["/səbˈstænʃl/"]/ 🇺🇸 /["/səbˈstænʃl/"]/
Meaning	Important or meaning a lot.	Large or important
Example	The research showed a significant improvement in patient outcomes.	substantial sums of money
Register	Neutral	Neutral
How common	Top 1,000 (very common)	Top 2,000 (common)
CEFR level	B2	C1
Part of speech	adjective	adjective
Collocations	be, prove, become, extremely, fairly, very, for, to	substantial amount, substantial evidence, substantial change, substantial increase, substantial support
Antonyms	insignificant, trivial, minor	insignificant, minor, trivial
Common mistakes	Confusing 'significant' with 'significance'., Using 'significant' as a noun instead of an adjective., Overusing 'significant' in casual speaking.	Confused with 'substantive' which has a different meaning., Using in place of 'significant' or 'important' without considering context., Overusing in casual contexts where simpler words like 'big' would fit better.
Usage notes	Used in academic and formal contexts to indicate importance. Avoid in very casual conversations; instead, use simpler words like 'big' or 'important'.	Use 'substantial' when describing something that is significant in size, quantity, or importance. It is appropriate in both spoken and written English but might be too formal for casual conversations.

See it in real clips

But of all these anomalies, the most significant is this:

But what is significant is, I felt the touch of God.

But of all these anomalies, the most significant is this:

But what is significant is, I felt the touch of God.

Significant

Frequently asked questions: Significant vs Substantial

What's the difference between Significant and Substantial?

Significant: Important or meaning a lot. Substantial: Large or important

Which is more common: Significant and Substantial?

Significant is the most common in everyday English.

Which is more advanced: Significant and Substantial?

Substantial is the highest level, at C1, on the CEFR scale.

Are Significant and Substantial the same CEFR level?

Significant: B2, Substantial: C1 on the CEFR scale.

What part of speech are Significant and Substantial?

Significant: adjective, Substantial: adjective.

Can you show an example of each?

Significant: The research showed a significant improvement in patient outcomes. Substantial: substantial sums of money

Can I use Significant and Substantial interchangeably?

Not always. Significant and Substantial are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.