hi

hi — exclamation

1. a friendly word you say when you meet or see someone you know — more casual and

1.exclamationA1
Definition

a friendly word you say when you meet or see someone you know — more casual and warmer than hello.

Example

Amelia smiled and said hi to her new classmates on the first day of school.

noun-like use: 'said hi' as object of verb

Hi, Bao! I did not expect to see you at this café today.

exclamation use: 'Hi, [name]!' with comma

Common collocations
  • say hi
  • shout hi
  • wave hi
  • mumble a hi
  • a quick hi
Synonyms
  • hello

    the standard, neutral greeting that works in both formal and informal settings

  • hey

    even more casual than hi, often used between close friends to get someone's attention

  • howdy

    regional American English, especially in the South and West; very informal

Antonyms
  • goodbye

    used when leaving or ending a conversation

  • bye

    the informal counterpart of goodbye, used in the same casual settings as hi

Usage Note

Frequently functions as a noun in expressions like 'say hi' or 'give a hi'. Unlike formal greetings such as 'good morning' or 'hello', hi is reserved for casual situations with people you already know. It is uncommon in formal letters, business emails, or when addressing someone in a position of authority.

Common Mistakes

Hi, Professor Chen' (in a formal academic context).
Good morning, Professor Chen' or 'Hello, Professor Chen
hi is too casual for formal or hierarchical situations.
Hi, I am writing to apply for the position' (in a job application email).
Dear Hiring Manager' or 'Dear Sir or Madam
hi is not used in formal written correspondence.

hi — abbreviation

hi — interjection

Synonym discussion

Sense: exclamation/1

All four words are greetings, but they differ in formality and regional use. 'Hello' is the most neutral and widely understood — it works in emails, on the phone, and with strangers. 'Hi' is warmer and more casual, best suited for people you already know. 'Hey' is even more informal than 'hi' and often carries a tone of surprise or an attempt to get someone's attention; it is common among close friends but can sound rude with strangers. 'Howdy' is limited to certain regions of the United States, especially rural areas in the South and West, and carries a folksy, friendly tone. For example, you might say 'Hello' to a new colleague, 'Hi' to a neighbour you see regularly, 'Hey' to a close friend across the street, and 'Howdy' only if you are in Texas or trying to sound deliberately rustic.

hello ↗hey ↗howdyhi ↗

Etymology

Middle EnglishEnglish

The greeting 'hi' likely developed from the Middle English exclamation 'hy' (pronounced 'hee'), which was used to attract someone's attention. A similar form appears in Old English as 'hīg,' an exclamation of surprise or call for attention. The modern casual greeting became popular in 19th-century American English, possibly influenced by the British 'hi!' used to hail someone from a distance. Over time, it overtook 'hey' as the standard friendly greeting and spread globally through American media and culture. The abbreviation senses (Hawaii, high intensity, humidity index, hemagglutination inhibition) are unrelated coinages from the 20th century that happen to share the same two letters.