o

A sudden expression used to convey surprise, enthusiasm, or a warm greeting, often employed to capture attention or signal a realization. It can also represent a poetic or archaic way of addressing someone directly.

• 🇪🇸Interjección repentina usada para expresar sorpresa, admiración, saludo o para llamar la atención, así como apelación poética.

1. Used to express surprise or strong emotion A1 informal

   An utterance that naturally occurs when a person experiences a sudden feeling of wonder, shock, admiration, or pain. It serves as an immediate vocal reaction before more structured speech is formed.

   • O, I didn't see you standing there in the dark!
   • She looked at the sunset and whispered, 'O, how beautiful it is.'
   • O, that really startled me—don't sneak up like that!
   • The crowd let out a collective 'O' as the fireworks exploded.
   • O, I just remembered where I left my keys!

   🇪🇸¡Oh! (interjección de sorpresa o emoción)

2. Used as a warm greeting or to attract attention A2 informal

   A friendly, often cheerful call meant to hail someone or draw notice. It appears in casual speech, songs, and festive declarations to establish a connection with the listener or audience.

   • O, there you are! We've been waiting for ages.
   • They sang, 'O come, all ye faithful,' in the candlelit church.
   • O, waiter! Could we get some more drinks over here?
   • He cupped his hands and shouted, 'O, is anyone out there?'
   • O, my dear friend, it's so wonderful to see you again!

   🇪🇸Oh (saludo o llamada de atención)

3. Archaic or poetic form of direct address C1 formal british art

   A stylized particle placed before a name or noun to invoke or entreat someone or something, commonly found in classical literature, prayers, and solemn speeches. It adds a dramatic, reverent, or romantic tone to the phrase.

   • O mighty king, grant us your wisdom in these dark times.
   • The poet wrote, 'O wild West Wind, thou breath of Autumn's being.'
   • O death, where is thy sting?
   • She recited, 'O Romeo, Romeo, wherefore art thou Romeo?'
   • O Lord, hear our prayer and deliver us.

   🇪🇸¡Oh! vocativo poético

The fifteenth letter of the English alphabet and the fourth vowel, representing a wide range of sounds including the long /oʊ/ as in 'go', the short /ɒ/ or /ɑ/ as in 'hot', and the reduced /ə/ as in 'button'. As a grapheme, 'O' is a symmetrical circle in its uppercase form and an oval in lowercase. It functions as an interjection of surprise, the chemical symbol for oxygen, a designation for zero, a blood type, and the fifteenth item in a sequence.

• 🇪🇸Decimoquinta letra del alfabeto inglés, vocal. Puede representar varios sonidos distintos. Como grafía, es un círculo simétrico. Se usa como interjección de sorpresa, símbolo químico del oxígeno, designación de cero y de grupo sanguíneo.

1. The fifteenth letter of the English alphabet A1 formal

   The uppercase or lowercase character (O, o) that constitutes the fifteenth symbol in the Latin-based English alphabet, classified as a vowel. It is a highly versatile letter representing multiple phonemes, including the diphthong /oʊ/, the short vowels /ɒ/ and /ʌ/, and the schwa /ə/. Its circular shape is one of the most recognizable in the alphabet, and the exclamation 'O' is often used poetically to express emotion.

   • The word 'open' begins with the letter O.
   • The letter O is shaped like a circle.
   • In the word 'hot', the O makes a short vowel sound.
   • She wrote a perfect round uppercase O.
   • The exclamation 'O dear!' expresses surprise or dismay.

   🇪🇸Decimoquinta letra del alfabeto inglés

2. The chemical symbol for oxygen B1 formal scientific

   The one-letter chemical symbol representing the element oxygen, atomic number 8. Oxygen is a highly reactive non-metal and oxidizing agent that forms compounds, most notably oxides, with most elements. As a diatomic gas (O₂), it makes up about 21% of Earth's atmosphere and is essential for respiration in most living organisms and for combustion.

   • Water is composed of hydrogen and oxygen, H₂O.
   • The patient was put on an O₂ mask to help with breathing.
   • Liquid O is used as an oxidizer in rocket propellants.
   • The level of dissolved O in the lake is critical for fish.
   • Ozone, O₃, is a molecule consisting of three oxygen atoms.

   🇪🇸Símbolo químico del oxígeno

3. The numeral zero A1 informal

   The letter or symbol O used interchangeably with the numeral 0 (zero) in spoken English, especially when reading sequences of digits aloud, such as phone numbers, room numbers, or years. While typed text typically distinguishes 0 from O, in speech and handwriting the two are often conflated. It represents the integer denoting a null quantity.

   • My phone number is five-five-five, oh-one-two-three.
   • The secret agent's codename is double-oh seven.
   • The room number is one-oh-four.
   • In the year nineteen oh-five, the city was founded.
   • He scored zero, or an 'oh', on the quiz.

   🇪🇸El cero

4. The blood type O B2 formal medical

   A classification of human blood based on the absence of A and B antigens on the surface of red blood cells, with both anti-A and anti-B antibodies present in the plasma. Individuals with type O negative are considered universal donors for red blood cells, while those with type O positive are the most common blood type. It is one of the four main ABO blood groups, inherited from parents.

   • O negative blood can be transfused into almost any patient.
   • She has type O positive, the most common blood type.
   • Hospitals urgently need O negative donors for emergencies.
   • My blood type is O, which I inherited from my mother.
   • Type O blood has no A or B antigens on the red blood cells.

   🇪🇸Grupo sanguíneo O

An informal spoken or written representation of the digit zero (0), using the letter name 'O' (or 'o') in place of the numeral; commonly used when reciting telephone numbers, room numbers, codes, years, and other sequences where clarity and rhythm are prioritized. Not a true numeral but a colloquial convention in both British and American English.

• 🇪🇸Forma oral o escrita informal de referirse a la cifra cero (0) usando la letra 'O'; se emplea a menudo al leer números de teléfono, códigos, años y otras secuencias.

1. Informal numeral substitute: the letter O representing zero A2 informal

   Used colloquially to represent the digit 0 when speaking or writing sequences such as phone numbers, account codes, room numbers, or years; valued for its brevity and phonetic clarity in rapid speech. Not appropriate in formal mathematical, scientific, or technical contexts where 'zero' is required.

   • My room number is two-one-O, not two-one-zero.
   • Call me at five-five-five-O-one-two-three.
   • The year nineteen-O-one marked the start of the century.
   • His employee ID ends in double-O.
   • The flight code is BA-O-O-seven.

   🇪🇸O (cero coloquial)

2. Noun: the letter O used as a zero symbol B1 informal

   A noun referring to the Latin letter O employed as a visual or auditory stand-in for the numeral 0; common in informal writing, texting, gaming handles, and spoken sequences where typographic distinction between O and 0 is not critical.

   • In the password, use an O, not a zero.
   • The license plate has three Os at the end.
   • He typed his username with Os instead of noughts.
   • The serial number mixes letters and Os for zeros.
   • In casual notes, she writes O for zero to save time.

   🇪🇸letra o usada como cero