the.com/scalar product

means A way of multiplying two vectors together that produces not another vector but a plain number, calculated by multiplying their lengths by the cosine of the angle between them (or, in coordinates, multiplying matching components and adding the results).

from 'Scalar' comes from Latin 'scalaris', 'of a ladder' (from 'scala', ladder or staircase), because such numbers can be placed in order along a single marked scale — like rungs — unlike vectors, which carry direction too. 'Product' is the ordinary arithmetic sense, from Latin 'productum', 'thing produced', going back to the 19th-century development of vector algebra by figures like Hamilton and Gibbs, who needed a name for the vector-multiplication result that collapsed back down to a mere quantity on the scale, not an arrow in space.