The number symbol fai is φ, and the lowercase is φ, which is the 2nd1letter of the Greek alphabet. The English pronunciation is phi, the international phonetic symbol /fai/. Represents magnetic flux, angle, lens power and heat flux. φ can be input with special characters of Sogou Pinyin input method. The specific method is as follows:

1, switch the input method to sogou input method;

2. Place the mouse cursor at any position in the taskbar of sogou input method, and then click the right mouse button;

3. On the pop-up page, click "Expression &; Symbol ";

4. Then click "Symbol Daquan";

5. Click Special Symbols/Greece/Latin in turn. There are 24 symbols with Greek letters in the first and second rows on the right. Click "φ" to enter.