咩係real number?

真有其數就是real number
如 1000, -51, 1.678, root 3, 7^2...
無其數不是real number
如 root (-3), log(-3), ln(-3)

1. 數,數字[C]
The number of students absent is five.
有五名學生缺席。
2. 號碼;第...號[C]
Sam lives at number 20 Park Street.
山姆住在派克街二十號。
3. 數量;總數[C][U][(+of)]
4. 一類人,一幫人[S]
He is not of our number.
他不是我們這樣的人。
5. 多數;數量上的優勢[P1]
Strength lies in numbers.
人多力量大。
6. 算術[P]
7. (雜誌等的)期,號[C]
His essay was carried in the June number.
他的散文登載在六月號上。
8. 演奏樂曲;上演節目[C]
Her numbers were well received.
她演唱的幾支歌曲很受歡迎。
9. 【口】一件衣服;一類事物之一[S1]
10. 【文】數[U]
11. 【俚】重複的演說,辯論或表演;老套
a heavy number
困難的處境;困難的情形
The suspects will do their usual number -- protesting innocence -- and then confess.
嫌犯們總會來他們的老套,先說他們是無辜的,然後才供認罪行。
vt.
1. 編號,給...號碼
These tickets are not numbered.
這些票上沒有編號。
2. 計入,算作[(+among/as/with)]
They numbered her among their best friends.
他們把她看作是最好的朋友之一。
3. 使為數有限[H]
The old man's days are numbered.
這位老人的日子屈指可數了。
4. 數...的數目
vi.
1. 總數達到,共計[L][Q]
Their readers number in the millions.
它們的讀者數以百萬計。
2. 計入,算作[(+among/as/with)]
He numbers among the best French playwrights.
他躋身法國最優秀劇作家的行列。

A real number may be either rational or irrational; either algebraic or transcendental; and either positive, negative, or zero.

Real numbers measure continuous quantities. They may in theory be expressed by decimal representations that have an infinite sequence of digits to the right of the decimal point; these are often represented in the same form as 324.823211247…. The three dots indicate that there would still be more digits to come.