1. Integer
Integers are whole numbers.
They can be positive, negative, or zero.
Examples: … -3, -2, -1, 0, 1, 2, 3 …
No fractions or decimals. So 1/2 or 3.4 are not integers.
2. Prime number
A prime number is a whole number greater than 1
It has only two factors: 1 and itself.
Examples: 2, 3, 5, 7, 11, 13…
2 is prime (only 1 and 2 divide it).
4 is not prime (1, 2, and 4 divide it).
3. Composite number
A composite number is a whole number greater than 1
It has more than two factors.
Example: 8 → factors are 1, 2, 4, 8 (so composite).
9 → factors 1, 3, 9 (composite).
Note: 1 is neither prime nor composite.
4. Even number
Any integer that can be divided by 2 with no remainder.
Ends in 0, 2, 4, 6, or 8.
Examples: 2, 4, 6, 8, 10, -4, -10.
5. Odd number
Any integer that cannot be divided evenly by 2.
Ends in 1, 3, 5, 7, or 9.
Examples: 1, 3, 5, 7, 9, -3, -7.
6. Decimal number
A number that uses a decimal point.
It shows a value between whole numbers.
Examples: 0.5, 1.23, 10.07.
7. Decimal point
The dot in a decimal number.
It separates the ones place from the places after the dot.
Example: in 3.14, the dot between 3 and 1 is the decimal point.
8. Decimal place
Tells how far a digit is from the decimal point.
Example: 0.123
1 is in the tenths place (first place after the dot).
2 is in the hundredths place (second place).
3 is in the thousandths place (third place).
9. Decimal (base 10) system
Our usual number system uses 10 digits: 0,1,2,3,4,5,6,7,8,9.
Every number we write uses these digits.
Example of another system: binary (base 2) uses only 0 and 1 (used by computers).
10. Rational numbers
Numbers that can be written as a fraction of two integers.
Includes: integers, fractions, and decimals that stop or repeat.
Examples:
5 → 5/1 (rational)
1/2 (rational)
0.75 ( = 75/100 ) (rational)
0.3333… repeating ( = 1/3 ) (rational).
11. Irrational numbers
Cannot be written as a simple fraction.
Decimal goes on forever and does not repeat in a pattern.
Example: π (pi) ≈ 3.141592… (keeps going, no pattern).
√2 is also irrational.
12. Real numbers
All rational numbers and all irrational numbers together.
Basically, any number that can be put on a number line.
Includes: integers, fractions, terminating/repeating decimals, and irrational numbers like π.
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