A writing system is the combination of a script (a visual representation of verbal speech, not to be confused with the “script” classification of typefaces) and a set of usage conventions (known as an orthography).
Scripts can be used by one or more languages. For instance, although English, French, German, Norwegian, and Portuguese are distinct languages—with their own alphabets, conventions, and diacritic usage—they all use the Latin script.
Other scripts include Greek (upon which Latin is based), Cyrillic (originally based on uppercase Greek forms), Arabic, Korean, Indic scripts from South and South East Asia, Han characters, and the traditional scripts of Africa.