1. The informal understandings of individuals (especially their social knowledge) which they have not verbalized and of which they may not even be aware, but which they may be inferred to know (notably from their behaviour). This includes what they need to know or assume in order to produce and make sense of messages (social and textual knowledge). Tacit knowledge is distinguished from explicit or formal knowledge and the term is sometimes used synonymously with common sense, in the sense of taken-for-granted knowledge. The concept is important in phenomenological sociology and ethnomethodology. It derives from Polanyi, who declared that ‘We can know more than we can tell.’
2. More specifically for Polanyi, our general awareness and holistic understanding which provide a background framework facilitating our deliberate focus of attention on specific phenomena. He sees such informal ‘personal knowledge’ as the foundation of all knowledge.