Which metric indicates how hard it is to rank for a certain keyword in organic search?

Keyword Difficulty (KD) is a metric that estimates how challenging it would be to rank in the top organic search results for a specific keyword. It's calculated based on various factors, including the authority of the ranking pages and the number of backlinks they have. A higher KD score indicates a more difficult keyword to rank for. Competitive density, while related to competition, typically refers to the number of advertisers bidding on a keyword in paid search, not organic ranking difficulty. Authority Score is a composite metric that measures a domain's overall influence and trustworthiness, but it doesn't directly quantify the ranking difficulty for a single keyword.