Since Autodesk no longer sells AutoCAD 2018 new, the content below is framed for (e.g., for a Mac running macOS High Sierra, Mojave, or Catalina).
If you have a valid license (perpetual or subscription that includes back versions): autocad 2018 for mac new
What's New in AutoCAD 2018 for Mac: Productivity Redefined The release of brings a suite of powerful updates designed to align the macOS experience more closely with its Windows counterpart while maintaining the sleek, intuitive feel Mac users expect. From performance boosts to interface flexibility, 1. Enhanced User Interface & Palette Management Since Autodesk no longer sells AutoCAD 2018 new,
If you need a but love the 2018 workflow: autocad 2018 for mac new