1. <mathematics> A single number, as opposed to a vector or matrix of numbers. Thus, for example, "scalar multiplication" refers to the operation of multiplying one number (one scalar) by another and is used to contrast this with "matrix multiplication" etc.
2. <architecture> In a parallel processor or vector processor, the "scalar processor" handles all the sequential operations - those which cannot be parallelised or vectorised.
See also superscalar.
3. <programming, PI> A data type in Perl combining what in many other languages is either a string or a number.
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