b 1 or B 
(bē)
(bē)n. pl. b's or B's also bs or Bs
1. The second letter of the modern English alphabet.
2. Any of the speech sounds represented by the letter b.
3. The second in a series.
4. Something shaped like the letter B.
5. B The second best or second highest in quality or rank: a mark of B on an English theme.
6. Music
a. The seventh tone in the scale of C major or the second tone in the relative minor scale.
b. A key or scale in which B is the tonic.
c. A written or printed note representing this tone.
d. A string, key, or pipe tuned to the pitch of this tone.
7. B One of the four major blood groups in the ABO system. Individuals with this blood group have the B antigen on the surface of their red blood cells, and the anti-A antibody in their blood serum.
This 14th-century French manuscript chronicles the travels of Marco Polo.