B : is the second letter of the English alphabet. (See Guide to Pronunciation, // 196, 220.) It is etymologically related to p, v, f, w and m , letters representing sounds having a close organic affinity to its own sound; as in Eng. bursar and purser; Eng. bear and Lat. ferre; Eng. silver and Ger. silber; Lat. cubitum and It. gomito; Eng. seven, Anglo-Saxon seofon, Ger. sieben, Lat. septem, Gr."epta`, Sanskrit saptan. The form of letter B is Roman, from Greek B (Beta), of Semitic origin. The small b was formed by gradual change from the capital B.

Example:
What's the difference Between A union B and A intersects B?

Taxonomy
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Defination from the web:
B, the second letter in the modern Latin alphabet. Includes notes on different meanings and uses of the letter.