A golf course is the dedicated playing field for golf, typically featuring 18 holes—each composed of a tee box, fairway, rough, hazards, and a green with a cup and flagstick—though 9-hole courses and other variations exist. Each hole is assigned a par (usually 3, 4, or 5) indicating the score a proficient player should achieve, which has led to specialized formats like par-3 courses and increasingly popular short courses. Worldwide, there are roughly 38,000–40,000 courses across 200+ countries, with the United States alone hosting over 40% of them; while many historic courses are coastal links built on natural sand dunes, modern ones can be private, public, or municipally owned. Golf course architecture is a distinct field, celebrated through designers like Alister MacKenzie and pro-golfer Jack Nicklaus, though membership in groups like the ASGCA is voluntary rather than a licensing requirement. Traditional layouts follow principles such as dividing play into the "front 9" and "back 9" (often labeled "out" and "in" on old links like the Old Course at St. Andrews), and architects carefully position greens near the next tee and vary hole lengths, occasionally even sharing fairways or greens in complex terrains.