2. Different units: the units of digits are: unit, ten, hundred, thousand, ten thousand ...; Counting units are: one, ten, one hundred, one thousand, ten thousand.
3, different meanings: 847, "8" takes hundreds as the unit, which means eight hundreds, and the counting unit is100; "4" is in the tenth place, which means four tens, and the counting unit is ten; "7" is in the unit, which means seven ones, and the counting unit is one.
Extended data:
The number of digits of an integer increases gradually from right to left: the first digit is a single digit, and the counting unit is one, indicating several ones; The second place is ten, and the counting unit is ten, which means several tens; The third place is hundred, and the counting unit is hundred, which means hundred; The fourth place is thousands, and the counting unit is thousands, which means thousands; The fifth place is 10 thousand, and the counting unit is 10 thousand, which means tens of thousands.
By analogy, it is very important for students to correctly understand the digits and counting units of integers and decimals, as well as the relationship between integers and decimals and the composition of numbers.