21B may refer to:
*
2-1B
In the ''Star Wars'' space opera franchise, a droid is a fictional robot possessing some degree of artificial intelligence''.'' The term is a clipped form of "android", a word originally reserved for robots designed to look and act like a human ...
, a droid character in ''Star Wars''
*
Boron-21 (B-21 or
21B), an isotope of boron
See also
*
B21 (disambiguation)
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