nine-tenths (9/10) equals 90%
Decimals are all ready decimals so how could you say to convert it back to decimal
terminating decimals and repeating decimals
Two of them are terminating decimals and recurring decimals
terminating decimals non terminating decimals repeating decimals non repeating decimals
The answer depends on what you wish to do with decimals.
Decimals is not a language!
Terminating decimals are decimals that end, such as, 2.384. Non-terminating decimals that don't end, such as, 0.3333333333.......
terminating decimals repeating decimals
Some decimals are. Counting numbers are a proper subset of decimals.
You need decimals when you measure and fractions. You need decimals, because to measure and fractions. Also, so whole numbers could exist if there are decimals. There will be no math if there's no decimals.