Obelus — Definition, Formula & Examples
Obelus is the proper name for the ÷ symbol, which represents division. When you see 12 ÷ 3, the little dash with a dot above and below it is called an obelus.
The obelus (plural: obeli) is a typographic glyph consisting of a horizontal line with a dot centered above and below it, adopted in mathematics to denote the division operation between two quantities.
How It Works
You read the obelus as "divided by." Place it between two numbers to show that the first number is being divided by the second. For example, means "20 divided by 4." In older grades, the obelus is the most common way to write division, but as you advance in math, the fraction bar or the slash ( / ) often replaces it.
Worked Example
Problem: What does 56 ÷ 8 mean, and what is the result?
Read the symbol: The ÷ (obelus) tells you to divide the number on its left by the number on its right.
Perform the division: Ask: how many groups of 8 fit into 56? Since 8 × 7 = 56, the answer is 7.
Answer: 56 ÷ 8 = 7
Why It Matters
Knowing the name "obelus" helps you communicate precisely about math notation. Standardized tests and textbooks sometimes refer to symbols by name, so recognizing this term avoids confusion when instructions mention the division symbol.
Common Mistakes
Mistake: Confusing the obelus ÷ with the minus sign −, since both involve a horizontal line.
Correction: The obelus always has one dot above and one dot below the line. If there are no dots, the symbol is a minus sign, which means subtraction, not division.