The term.
Its weight -- a frequency, a score, a count.
Widened to accept a string for the same reason BarPoint.y is:
hand-authored JSON and some producers send numbers as strings, and the
trace coerces on the way in. Declaring it number alone would not stop
one arriving, it would only stop the compiler from admitting it -- and a
string reaching the description's running total would concatenate rather
than add.
One term of a word cloud.
A word cloud is the canonical chart that carries real data while being readable only by eye: the weight is encoded as glyph size and written down nowhere on the page. Structurally it is a categorical label and a magnitude, which is why it needs no shape of its own beyond naming them.