Question

How we can say that a wire is 1D as it is like a cylinder ?

Answer 1

One Dimension: Once you connect two points, you get a one-dimensional object — a line segment. A line segment has one dimension: length.

Here the wire has just one dimension, its length.So its considerd as one dimensional.

But cylinder has another 2 dimensions. Height and radius.
Cylinder is a 3D object.