Forbidden vs Unconstitutional

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

Forbidden

FormalTop 3,000 (common)

Unconstitutional

FormalBeyond 10,000 (less common)B1adjective
Most common: Forbidden
 ForbiddenUnconstitutional
Pronunciation🇬🇧 //fəˈbɪd.ən//🇺🇸 //fərˈbɪd.ən//🇬🇧 /["/ˌʌnˌkɒnstɪˈtjuːʃənl/"]/🇺🇸 /["/ˌʌnˌkɑːnstɪˈtuːʃənl/"]/
MeaningNot allowed or banned.Not allowed by the constitution of a country.
ExampleThe secret room was strictly forbidden to anyone except the owner.The judges declared the decision unconstitutional.
RegisterFormalFormal
How commonTop 3,000 (common)Beyond 10,000 (less common)
CEFR level-B1
Part of speechadjective
Collocationsforbidden zone, forbidden love, forbidden activities, forbidden fruit, forbidden cityunconstitutional law, unconstitutional action, declare unconstitutional
Antonymsallowed, permitted, legalconstitutional, legal
Common mistakesConfused with 'prohibited' - both mean similar things, but 'forbidden' is less formal., Incorrectly used as a verb - 'forbidden' is strictly an adjective., Using 'forbidden' in positive contexts - it always suggests something disallowed.Confused with 'illegitimate' when they are not exactly the same., Using it in non-legal contexts., Incorrectly conjugating as a verb.
Usage notesUsed to describe something that is legally or socially unacceptable. Avoid using in casual conversations.Use 'unconstitutional' in legal and formal contexts when referring to laws or actions that violate a constitution. Avoid in casual conversations.

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Forbidden

Frequently asked questions: Forbidden vs Unconstitutional

What's the difference between Forbidden and Unconstitutional?

Forbidden: Not allowed or banned. Unconstitutional: Not allowed by the constitution of a country.

Which is more common: Forbidden and Unconstitutional?

Forbidden is the most common in everyday English.

Can you show an example of each?

Forbidden: The secret room was strictly forbidden to anyone except the owner. Unconstitutional: The judges declared the decision unconstitutional.

Can I use Forbidden and Unconstitutional interchangeably?

Not always. Forbidden and Unconstitutional 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.