I was talking to my friend (native Chinese) the other day and when she read out a phone number she said "yao" for all the "ones" in the phone number.
However, as far as I remember, for all other cases she says it normally - eg. "yi ge" when counting etc.
Also, as far as I know, people from Taiwan don't use "yao" but stay with "yi" for all cases of uses of the number "one".
Does anyone know why "yao" is used instead of "yi"?
In the mainland of China (I don't know how people in Taiwan use this character, sorry), people usually use "yao" when reading numerical serial numbers, digit by digit. One typical application is the phone number. In almost all other cases, only "yi" should be used.
Why can it mean "one"?
The character for "yao" is "幺". Which originally (in classic Chinese) means "young,little". Especially this meaning is used (still used nowadays, very popular here in Chengdu) to refer to the youngest child in a family.
I believe the meaning "one" extends from this meaning, since 1 is the "youngest" element in natural number family (without 0).
Why is it used as "one"?
As Bathrobe pointed out, once this was very popular in military actions, to avoid the misunderstanding as 七, to express the numbers more clearly.
My understanding is that it is originally a military usage. Since the pronunciation yī is easily mistaken for 七 qī in radio transmissions etc, yāo is substituted in the interest of aural clarity.
This usage is not found in Taiwan (although I can't speak for the Taiwanese military).
This question has been answered before.
Yes, yi is pronounced as yao in a series of telephone numbers to avoid being confused with qi (which is seven).
And yi (one) is not the only number which has a new pronunciation. In the military in China, I believe 170 is pronounced as 一 yao, 七 guai, 零 0 dong.
Something similar happens in English. Don't native speakers of English read 5 0 9 as five "oh" nine instead of the more accurate "five zero nine"?
Ask any accountant how to pronounce "509," and most professionals would say "five zero nine" and not "five oh nine."
In all languages, there are variations in pronunciation due to location and profession. E.g., Houston, Texas versus Houston St (Howston St) in New York City.
你是谁？ "Ni shi shei?" versus "Ni shi shui?" (usually in a small area in Northern China. Two of my acquaintances say "shui."
We learn more when we ask more questions such as
"Who says this?" "Under what circumstances" "How often?"
"Ya, understand where I am comin' from, eh?"
Language often indicates class, level of education, group association, etc.
Also, many people just speak a language without understanding the several messages that the words may give. If we change the tone of our voice or use sarcasm, we can change the meaning of the words.
This is what makes learning Chinese so exciting. Because the Chinese characters are ambiguous, and therefore the speaker can play with the meaning of the sound/character.
Also, because the pronunciation of a word can be interpreted in many ways, that may lead to confusion or more often a joke.
