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The abbreviations 2D and 3D stand, respectively, for two-dimensional and three-dimensional – adjectives describing the spatial extent of physical objects, geometrical figures, digital images, or, in fact, any entity having a measurable size. Before explaining the difference between 2D and 3D, it is important to explain briefly what exactly is meant by dimension.

In ordinary language, dimension can simply be defined as ‘any measurable spatial extent, such as length, breadth, height, depth, width, thickness, etc.’

With this definition of dimension, 2D describes an entity having two dimensions and 3D describes an entity having three dimensions. For example, a flat sheet of paper is two-dimensional (having length and breadth), with thickness assumed to be negligible, but when it is folded to make a paper box it acquires one more dimension, that of depth. A box is, therefore, said to be three-dimensional. Extending the same logic, a strand of hair is thus one-dimensional (assuming the thickness to be negligible).

Similarly, talking of geometrical shapes and figures, a line drawn on a sheet of paper is 1D, shapes like rectangle, square, triangle, polygon, etc., are 2D, and those like cylinder, sphere, cube, pyramid, prism, etc., are 3D. Another example elucidating the difference between 2D and 3D is from the field of arts – that of a painting and a sculpture. A painting (on canvass or whatever) is 2D and a sculpture is 3D. A photograph of a real 3D object, say a car, is its 2D representation.

In the technical language of physicists and mathematicians, the dimension of an object is defined as the minimum number of coordinates required to locate and specify any point on/in it. Thus, any geometrical figure lying in a plane (other than a line, which is 1D, because only one of the coordinates xyz is required to specify any point on it) is 2D, because at least two of the coordinates xyz are required to specify any point on it. Any 3D object in space requires all the three xyz coordinates to be specified to locate a point on/in it.

The additional dimension gives the perception of depth to a flat object and allows for rotation. To sum up, the main points of difference between 2D and 3D are:

• 2D entities have two measurable dimensions, while 3D have three.
• 2D objects/ images lie in a plane (or could also be a curved surface) and look flat, 3D ones are extended into space beyond the 2D plane/surface, i.e., they lie in 3D space, and give the perception of depth.
• 2D figures are characterized by two dimensions and area, whereas 3D figures are characterized by three dimensions and volume.
• Rotation of a 3D object can show different perspectives, but not so for 2D.

That’s all about the difference between 2D and 3D.

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