1. **State the problem:** From the set \(\left\{\frac{22}{7}, 3.14, \pi\right\}\), write down an irrational number. 2. **Recall definitions:** - A rational number can be expressed as a fraction of two integers. - An irrational number cannot be expressed as a simple fraction and has a non-repeating, non-terminating decimal expansion. 3. **Analyze each number:** - \(\frac{22}{7}\) is a rational approximation of \(\pi\). - \(3.14\) is a decimal approximation, rational because it can be written as \(\frac{314}{100}\). - \(\pi\) is a well-known irrational number. 4. **Answer:** The irrational number is \(\pi\). **Final answer:** \(\pi\)