A more thorough explanation:

Definition: Common substitution is the process of designating a person or thing to take the place of another person or thing. It can refer to:

1. Replacing one or more words with others in an amendment in parliamentary law.
2. The nomination of a person to take the place of a previously named heir who has refused or failed to accept an inheritance in Roman law.
3. The nomination of a person to succeed a descendant who is under the age of puberty and in the potestas of the testator, if the descendant has died before reaching puberty in Roman law.
4. A testator's designation of a person to whom the property was to be given by the person named as heir, or by the heir of that person in Roman law.
5. The designation of a person to succeed another as beneficiary of an estate, usually involving a fideicommissum in civil law.

For example, in parliamentary law, an amendment by substituting one or more words with others is a common substitution. In Roman law, if a descendant has died before reaching puberty, a person can be nominated to take their place as a successor. In civil law, a person can be designated to succeed another as a beneficiary of an estate.

Overall, common substitution is the process of replacing one person or thing with another in various legal contexts.