Meaning of O in English

O

I. O 1 BrE AmE , o /əʊ $ oʊ/ noun ( plural O’s , o’s )

1 . [uncountable and countable] the 15th letter of the English alphabet

2 . [uncountable] spoken zero:

My phone number is six o four double two (=60422) .

3 . [uncountable] a common type of blood

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THESAURUS

▪ zero the number 0. Also used when saying there is nothing at all:

A million is written as one followed by six zeros.

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a temperature of zero degrees

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Our chances of success are virtually zero.

▪ nil British English zero - used especially in the results of sports games:

United won the game three-nil.

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In rural areas, employment opportunities are almost nil.

▪ nought British English spoken zero – used in calculations and figures:

It has increased by nought point seven five per cent (=0.75%) .

▪ O used to say the number 0 like the letter O:

The code for Oxford is 0 one eight six five (=01865) .

II. O 2 /əʊ $ oʊ/ BrE AmE interjection

[ Date: 1100-1200 ; Origin: Natural sound ]

1 . used when praying to a god or, in the past, when speaking to someone in great authority:

O Lord, in you I put my trust.

2 . another form of ↑ oh

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.