 # Homework tips: vital geometry vocabulary to remember

To understand the complicated geometry terms, you need to understand the basics first. Here are 15 basic geometry terms to help you get a decent foundation for everything else.

• A line
• A straight line drawn at any angle.

• A plane
• This is a two-dimensional platform. It has length and breadth, but no depth.

• A foot
• When a line intersects with a plane, that is called a foot.

• A parallelogram
• A shape that has four sides. Each side has the same length as its opposite counterpart.

• Diagonal
• When a closed shape has a line on the inside of it that stretches from one corner to another, that line is called a diagonal. Note that this does not apply to two corners that are next to each other—because drawing a line form one corner to the one next to it is called an edge; therefore this can only be done on a shape that has four or more corners.

• Bisect
• A dividing line drawn across lines, corners, and/or shapes.

• A square
• Where all four sides are perfectly perpendicular to each other in length. All four corners are also exactly 90 degrees.

• A triangle
• A closed shape with three sides and three corners. All three corners of a triangle will always make up 180 degrees.

• A coplanar
• A 2 dimensional surface that is shaped like a triangle.

• An incenter
• If you bisected a triangle from each corner and met each line in the middle, you could then draw a perfect circle which would connect the three points of the lines that meet each side. This is called the incenter.

• Perpendicular
• Where two opposite sides are symmetrically lined up with each other.

• A kite
• Imagine the shape of a kite. It has two short sides that are the same length and perpendicular to each other. Then it has two more sides that are longer, but also the same length and perpendicular to each other.

• Altitude of a triangle
• When you pull a line from one corner of a triangle to its adjacent side, that line refers to the altitude of a triangle.

• Orthocentre
• If you did the above with all three corners, the middle point of the triangle would be called the orthocentre.

• Collinear
• Two points that appear on the same line are called collinear.