||A public language contrasts with a private language (a language only one person can speak, or know that they speak) and an idiolect (a language whose properties are determined by properties of the individual speaker, rather than other speakers or the community of speakers as a whole). Three main questions concerning public languages are the following. First, are there public languages, or are languages invariably either private languages or idiolects? Second, if there are public languages, are there languages that are not public, so either private languages or idiolects? Third, if there are both public languages and languages that are not public, what is the relation between private and public languages?