Speech in this loose sense is the communication or expression of human thoughts and emotions, including requests, offers, assertions, beliefs, declarations, concepts, moods, and feelings. A notational system is a set of symbols and conventions used in a more or less uniform way by a body of people. By contrast, encryption is a method of concealing expression. The objective of encryption is not to communicate or even to facilitate communications, but rather to hide one's communications. To obtain the communications, the effect of the encryption must be undone through decryption.
Encryption thus is a privacy enhancing technology.
Encryption has been compared with using a foreign language. But it is nothing like a foreign language because there are no constructs for expressing thoughts or emotions in ciphertext directly. Instead, one must express thoughts and emotions in some ordinary language and then transform the communication into ciphertext through encryption. Encryption and decryption are not like translations between English and French because there is no regard to meaning or interpretation of the bits. Encryption and decryption are simply bit transformations that have the property of cancelling each other.