One plus one

One plus one (1+1) can mean many different things, depending on the mathematical system under consideration. Many algebraic structures have some operation which is called, or equivalent to, addition, and an element called, or equivalent to, one.

 Modulo 2/XOR      1+1=0
 Binary OR/AND     1+1=1
 Binary            1+1=10
 Golden mean base  1+1=10.01
 Balanced ternary  1+1=11
 Negabinary        1+1=110
 Binary i-1 base[?]   1+1=1100
 Decimal           1+1=2
 Biology           1+1=3
 String literal    "1"+"1"="11" (concatenation)

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There are also films, companies and many other things called one plus one or one and one

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A Chinese joke: What is "1+1"? Answer: 王 (wang).