We think of knowledge as something that can be recorded in words, visualized and taught. However, this isn’t always the case. Tacit knowledge is a class of knowledge that’s difficult to communicate. Tacit knowledge is knowledge that’s difficult to write down, visualize or transfer from one person to another. Tacit knowledge is a particular challenge for knowledge management. Firms would like to prevent knowledge loss due to employee turnover. However, tacit knowledge almost always goes with the employee. Tacit knowledge is essential to competitive advantage because it’s difficult for competitors to copy. It’s the reason some firms pump out innovation after innovation while other firms struggle.