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### Course: Early math review>Unit 8

Lesson 2: Properties of shapes

# Recognizing shapes

Learn about recognizing and naming different shapes, such as circles, ovals, triangles, and various types of quadrilaterals like rectangles, squares, rhombuses, and trapezoids. The video explains the properties of each shape and how to distinguish them from one another.

## Want to join the conversation?

• Can someone help with remembering the names for 123456789?
• do you mean the prefixes? Here:

1 uni/mono - think about unicorns or monloges
2 bi - think about bicycles
3 tri - tricycles
4 tetra - if you play tetris, you'll know it!
5 penta - sorry, I don't really have one for this...
6 hexa - just remember that if it starts with a 'h', it's either 6 or 7. And since 'hexa' contains the letter 'x', you know it is six. Seven is simply the other one :)
7 hepta - refer to above
8 octo - octopus
9 nona - sounds like nine, doesn't it?

Hope this helps!!
• can any one help me with remembering what tri and uni and octi quad and hex and other things like that?
• You can remember the prefix `tri-` with the word `tricycle`, as it is a bicycle, but with `3` wheels. A `triangle` has `3` sides and angles. See more below:
`Octi-` as in `octopus`. An `octopus` has `8` arms, and an `octagon` has `8` sides and angles.
`Quad-` as in `quad-bike`. A `quad-bike` has `4` wheels, and a `quadrilateral` has `4` sides and angles.
`Hex` I'd just memorize. :)
Need any more help? Just say so! :)
• What does "hex" mean?
• "Hex" or "hexa" is a prefix that means 6 of something.
• What Sal mean " these will cross the other opposite side " when he explain trapezoids ?
• He means that those two line segments are not parallel. If you were to lengthen them, eventually they would intercept each other, or cross, as Sal says.
• How do they come up with the names of the shapes?
• Many of the shape names depend on how many sides the shape has. The prefixes, such as quad-, penta-, hexa-, come from greek numbers to show the number of sides.
• Is anything with four "equal" sides a rhombus?
• A shape with four equal sides is called a square. A square is a rhombus because a rhombus is a quadrilateral with all sides equal in length. A square is a quadrilateral with all sides equal in length and all interior angles right angles. Thus a rhombus is not a square unless the angles are all right angles. A square however is a rhombus since all four of its sides are of the same length.
• what do you call a shape with a hundred sides?
• A hundred-sided polygon is called a hectogon.

The word hectogon is a combination of the following Greek roots:
- hecto = 100
- gon = side

A thousand-sided polygon is called a chiliagon. This word is derived from the Greek word "chilioi", meaning 1000. (Our prefix kilo also comes from the root "chilioi".)

Hope this helps!
• at , wouldn't the shape be a parallelogram and not a rhombus?
• a rhombus is a parallelogram , but the parallelogram is not always a rhombus.
• Hello,
I was wondering if a triangle and hexagon are 3D shapes?
• A triangle is a 2d shape and so is a hexagon. 3d shapes have depth. A 2d shape does not.
• Getting into the origin of words, triangle means 3(tri) angles.
Similarly in quadrilateral, the quad is supposed to mean 4, but what is lateral supposed to mean here?
And what about circle? Why is the shape called a circle?