Explanation
In this lesson, we learn the difference between \(1D, 2D,\) and \(3D\).
The word dimension tells us how many pieces of information we need to describe or locate something.
\(1D\): One-Dimensional Space
\(1D\) means one-dimensional.
A \(1D\) space is like a line, such as a number line.
In \(1D\), you can move only in one direction:
right or left
A point on a number line needs only one number to locate it.
For example:
\(x = 3\)
So, 1D has only one measurement:
length
Axis direction:
🔵 \(x\)-axis → right / left
\(2D\): Two-Dimensional Space
\(2D\) means two-dimensional.
A 2D space is a flat surface, like the coordinate plane.
In 2D, you can move in two directions:
right or left
up or down
A point in \(2D\) needs two numbers to locate it:
\((x, y)\)
Axis directions:
🔵 \(x\)-axis → right / left
🔴 \(y\)-axis → up / down
Examples of \(2D\) shapes include:
• square
• rectangle
• triangle
• circle
So, \(2D\) shapes have:
length and width
\(3D\): Three-Dimensional Space
\(3D\) means three-dimensional.
A \(3D\) space is the space around us.
In \(3D\), you can move in three directions:
right or left
forward or backward
up or down
A point in \(3D\) needs three numbers to locate it:
\((x, y, z)\)
Axis directions:
🔵 \(x\)-axis → right / left
🔴 \(y\)-axis → forward / backward
🟢 \(z\)-axis → up / down
Examples of 3D solids include:
• cube
• cuboid
• sphere
• cone
• cylinder
• prism
So, \(3D\) objects have:
length, width, and height
Formula / Rule
A simple way to remember the difference is:
\(1D\) → one number → \(x\)
\(2D\) → two numbers → \((x, y)\)
\(3D\) → three numbers → \((x, y, z)\)
Another way to remember it:
\(1D\) → a line
\(2D\) → a flat shape
\(3D\) → a solid object
Examples
Classify each object as \(1D, 2D,\) or \(3D\).
Example 1
A number line.
A number line is a line.
You can move only right or left.
So, a number line is:
\(1D\)
Example 2
A square.
A square is a flat shape.
It has length and width, but no depth.
So, a square is:
\(2D\)
Example 3
A cube.
A cube is a solid object.
It has length, width, and height.
So, a cube is:
\(3D\)
Video Explanation
Practice
Continue Learning
- Length, Area, and Volume: What’s the Difference?
- Difference between \(1D, 2D,\) and \(3D\) (Current lesson)
- \(3D, 4D,\) and Beyond in Real Life