The Experience reference article from the English Wikipedia on 24-Apr-2004
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Experience

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Experience is knowledge of and skill in something gained through being involved in or exposed to it over a period of time. It generally refers to know-how or procedural knowledge, rather than propositional knowledge. Knowledge based on experience is also known as empirical knowledge or a posteriori knowledge. A person with considerable experience in a certain field is called an expert.

If someone is recounting an event they witnessed or took part off they are said to have had a "First hand experience".