What Is Sui Generis (Legal Use and Definition)

What is the definition of sui generis?

What does the legal term sui generis mean?

In law, when do you use this term?

In this article, we will break down the meaning of sui generis so you know all there is to know about it.

We will provide you with the origin of the term, its legal definition, how you use it in a sentence, when it is used in law and more.

Are you ready?

Let’s get started!

Sui generis 

What does sui generis mean?

Sui generis is a Latin term to refer to something that is of in its own class or some on-of-a-kind.

Sui generis origin 

The term sui means “its own”.

Generis comes from the Latin root “genus” that can be translated into English as “kind” or “class”.

Sui generis is therefore “of its own kind”.

The term “sui generis” is used in many disciplines, including law.

For example, when the court interprets a legal concept in a new way, it may use the term sui generis to indicate that this interpretation is unique. 

Sui generis definition 

According to Cornell Law School’s Legal Information Institute taking the definition from Nolo’s plain-English Law Dictionary, sui generis is defined as follows:

“Latin for of its own kind, and used to describe a form of legal protection that exists outside typical legal protections — that is, something that is unique or different”

Under this legal definition, sui generis is defined to be a legal concept or protection that is unique.

Sui generis variations

We may see different variations of the term sui generis, such as:

  1. Suigeneris
  2. Sui-generis
  3. Suis generis 
  4. Sui generi

These are incorrect variations of the term.

The proper spelling is “sui generis”.

Use in a sentence

You can use the term sui generis as an alternative to the term “unique”.

For example, you can use sui generis in a sentence as follows:

This case leads the court to a sui generis interpretation of the law

The same sentence could have been written as:

This case leads the court to a unique interpretation of the law

Another example is:

This man has sui generis skills

Sui generis pronunciation

Sui generis is pronounced as “soo-ee generis”.

Use of sui generis in law

Typically, the term sui generis is used by the courts to refer to a case, a legal concept or doctrine that is unique.

For instance, a judge may say the interpretation of a case is sui generis or a certain legal concept is sui generis.

That means that the facts of the case are unique or the legal concepts are unique and cannot be classified with other concepts.

A court may indicate that a case is sui generis where it’s unique rationale should not be applicable to the principles of stare decisis.

If a case is sui generis, it means that it is so unique that its underlying rationale may not be interpreted broadly.

Sui generis example

Duhaime’s Law Dictionary provides an interesting example of how the term sui generis can be used in law.

The example they cite is with respect to the Canadian court discussing the legal status of a treaty between the First Nations of North America and European settles.

The Canadian Supreme Court wrote that a:

“treaty with the Indians is unique, that it is an agreement sui generis which is neither created nor terminated according to the rules of international law.”


Sui generis is something unique and of-its-own-kind or of-its-own-class.

The term is used in law to refer to a unique doctrine, unique factual underpinnings of a case, unique rationale or interpretation of a legal concept, unique legal remedy or something that cannot fit with an existing class or concept.