The decimal numeral system has ten as its base. A decimal number, or just a decimal, refers to any number written in decimal notation.
One hundred or 100 is the natural number following 99 and preceding 101.
One thousand or 1000 is the natural number following 999 and preceding 1001. In most English-speaking countries, it is often written with a comma separating the thousands unit: 1,000.
Decimals: 0.10 = 1/10, 10/100; 0.01 = 1/100; 0.001 = 1/1000; etc.
Hundreds: 100 = one hundred; 200 = two hundred; 500 = five hundred; etc.
Thousands: 1000 = one thousand; 10,000 = ten thousand; 100,000 = one hundred thousand; etc.
Millions: 1,000,000 = one million; 10,000,000 = ten million; 100,000,000 = one hundred million; etc.
- 125 = a/one hundred and twenty five;
- 5 459 095 = five million four hundred and fifty nine thousand and ninety five.
- We can use either “a” or “one” at the beginning of a number (from 100 and on);
- When we say numbers we don’t use the plural.
In formal writing it is better to write the number in letters.