A more thorough explanation:

Definition: A defect of substance is a mistake or error in the essential part of a legal document. This can happen when an important term or detail is left out, making the document incomplete or invalid. It is different from a defect of form, which is a mistake in the way the document is written or presented.

Example: A contract for the sale of a car that does not include the make, model, or year of the vehicle would be considered a defect of substance. Without this information, the contract is incomplete and cannot be enforced.

Another example: A will that does not name any beneficiaries or heirs would also be a defect of substance. The purpose of a will is to distribute a person's assets after their death, and without naming beneficiaries, the will cannot fulfill this purpose.

These examples illustrate how a defect of substance can render a legal document invalid or unenforceable. It is important to carefully review and ensure that all essential details are included in any legal document to avoid such defects.