Thereto/ˌðerˈtuː/ Definition 1 of 1Pro Tip 1/3Legal Context Often used in legal, formal, or technical writing to refer to a previously mentioned subject. The rights of the parties thereto shall be respected. Pro Tip 2/3Old-fashioned 'Thereto' can sound outdated; modern English typically uses simpler terms like 'to it' or 'to that'. She added her signature to that. Pro Tip 3/3Precision Use 'thereto' for precise reference to something specific mentioned earlier. A clause was appended thereto for clarification.