ARC (Authentic use – Restricted use – Clarification and focus) is a way of describing what happens in a language lesson, proposed by Jim Scrivener. Unlike PPP, it is not a template for building a lesson. It names three kinds of classroom work and leaves the teacher free to use them in any order and any combination.
Authentic use covers any stage where learners meet or produce language the way it is used outside the classroom, with attention on meaning and message rather than on accuracy. A free discussion, or reading a text for what it actually says, both count. This is the communicative pole of the model.
Restricted use is controlled, accuracy-focused practice in which the language learners can produce is deliberately narrowed: drills, gap-fills, substitution tables, controlled questions. It corresponds closely to the Practice stage of other models.
Clarification and focus is where attention is drawn to a piece of language and its meaning, form, and pronunciation are explained or highlighted, whether through teacher presentation or guided discovery. Corrective feedback on errors belongs here too.
The point of ARC is that these are categories, not steps. Where PPP prescribes a fixed forward order, ARC describes whatever is happening at a given moment and lets the teacher decide what a particular class needs. A lesson might run A-R-C, or C-R-A, or loop through R-A-C-R-A. A conversation class leans toward authentic use, a grammar lesson toward clarification, and the model passes no judgement on which is right. Its value is as a planning and analysis lens, a checklist for asking whether learners are getting the balance of real use, controlled practice, and explicit focus that the lesson aim calls for.
Seen this way, ARC absorbs rather than rivals the other staging models. Test-Teach-Test is simply an authentic-use diagnostic followed by clarification and renewed use, and the flexible reorderings of Harmer's ESA map onto the same freedom. What distinguishes ARC is that it is the most purely descriptive of the family, built to evaluate any lesson's staging rather than to generate one.