Understanding the Plus Sign (+)
The plus sign is so familiar that most people never stop to think about it. Yet it is one of the most powerful symbols in all of mathematics, carrying a precise meaning every time it appears.
History of the Plus Sign
The + symbol was first used by German mathematician Johannes Widmann in 1489 in a book about trade arithmetic. It spread across Europe over the following century. Before then, mathematicians wrote words like "et" (Latin for "and") or abbreviations such as "p" to show addition.
What the Plus Sign Means
The + symbol between two numbers tells you to combine them. It is an operator — a symbol that specifies an action to be performed.
The Plus Sign in Different Contexts
| Context | Meaning | Example |
|---|---|---|
| Arithmetic | Add two numbers | 7 + 5 = 12 |
| Positive number | Shows a number is positive | +3 means positive 3 |
| Algebra | Add terms | 3x + 2y |
| Concatenation (programming) | Join strings together | "Hello" + "World" = "HelloWorld" |
| Grades (informal) | Slightly above | A+ means slightly better than A |
Reading Expressions with the Plus Sign
The + sign is read as "plus" or "add" in everyday maths. In more formal contexts, it might be read as "and" or "increased by".
- 8 + 3: "eight plus three" or "eight add three"
- x + 5: "x plus five" or "x increased by five"
Multiple Plus Signs
You can chain several additions together. The associative property means the grouping does not change the final total.
Key Takeaways
- The + symbol was first used in 1489 to mean addition.
- As an operator, it tells you to combine amounts.
- As a sign, + in front of a number indicates it is positive.
- The same + symbol is used in algebra, programming, and informal grading.
Practice Questions
- In 14 + 9 = 23, what role does the + play?
- What does +7 mean when it appears in front of a number with no other context?
- Rewrite the expression "the sum of 6 and 11" using the + symbol.
- Calculate 4 + 9 + 6 + 1 by grouping conveniently.
- Why is the + symbol also used to show positive numbers?