Ask Dr. Math

Elementary School Archive

Browse Elementary School Definitions
Stars indicate particularly interesting answers or good places to begin browsing.

Selected answers to common questions:
    Meters squared or square meters?
    Greater than, less than symbols.

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Symmetry [04/29/2001]

What is symmetry?

Telling Time: A.M. and P.M. [10/30/2001]

What do A.M. and P.M. mean?

Three IS Greater Than Two? [10/21/2002]

Should we say '3 greater than 2' or '3 IS greater than 2'?

Trilogy, Tetralogy... [05/28/2003]

Why isn't there a numbering system for groups like trilogies?

Truncating [01/19/2002]

What does truncating mean?

Types of Triangles [02/24/2003]

What is the the difference between equilateral, isosceles, and scalene triangles? How can I remember which name goes with which triangle?

Use and Meaning of 'And' in Naming Decimals [12/01/2004]

Can you please tell me what the word "and" means in the word form of a decimal number?

Vertical Angle [11/15/2001]

What are vertical angles? Are they equal?

What Does a Twofold Increase Mean? [01/23/2004]

Is a twofold increase simply twice the amount? What about a threefold increase? I'm not used to this terminology of using 'fold.' Does it refer to powers or multiples?

What is a Multiple? [12/4/1995]

What is the definition of a multiple?

What is a Parenthesis? [07/17/2000]

What does the mathematical term "parenthesis" mean?

What is a Set? [04/04/1997]

What is the correct term to refer to groups of objects like 3 cars, 7 pencils, or 5 apples?

What is a Sign? [04/21/2003]

Can you do anything in math without signs?

What is a Significant Digit? [12/25/2001]

I came across a question asking for an answer with no more than "2 significant digits" - can you please explain what a significant digit is?

What is a tessellation? [01/20/1997]

Can you give an example?

What is a Torus? [11/30/1999]

Is there a good way to describe a torus to a child?

What is a Vertex? [12/06/2001]

And what does vertices mean?

What is Circumference? [06/25/2001]

My friend told me it's somewhat like the measurement of the outside of a circle, but I don't understand that.

What is Length in a Rectangle? [05/31/1999]

Is the length of a rectangle the longest side, whether vertical or horizontal?

What is the Plural of Rhombus? [4/7/1995]

Hi! Say, what exactly is the plural of "rhombus?" We aren't sure if it is "rhombi" or "rhombuses".

Who Invented the Square Root? [12/11/1996]

I've only seen long, stringy roots!

Whole Numbers and Multiples [09/11/2001]

My students and I have been trying to figure out what numbers are in the set of "Whole Numbers." Is zero a whole number?

Why Does 1 Degree Equal 60 Minutes? [07/28/2004]

In 60 minutes, the minute hand of a clock makes a full circle, which is 360 degrees. How can 60 minutes equal 1 degree when measuring angles?

Why Is a Circle 360 Degrees? [07/01/1998]

Why is a circle defined as 360 degrees?

Why Is 'Pound' Abbreviated 'lb'? [03/08/2004]

Why is "pound" abbreviated lb? Is it because of its Latin roots? I know libra means pound. What is the history of it?

Why is the Word "Number" Abbreviated to "No."? [05/13/2002]

Why is the word number abbreviated to no.?

Word for a 225th Birthday [07/10/2001]

This year America is celebrating its 225th birthday. As we celebrated the bicentennial in 1976, is there a term for 225 years?

Writing Numbers with Hyphens [06/04/2003]

Why do we hyphenate one hundred-millionth, but we don't hyphenate one hundred million?

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