someone

The word “someone” means an unspecified or unidentified person. In plain terms, an unnamed or unknown person.

“Someone” is pronounced SUHM-wuhn (/ˈsʌmwʌn/ in IPA).

Here is “someone” used in a sentence: “Someone knocked on the door late last night.”

“Someone” is a pronoun.

The word “someone” comes from Middle English. From Middle English sum on, "some one".

“Someone” is a very common word in modern English, usually learned at around the A1 level.

There is no difference in meaning — both refer to an unspecified person, and they are fully interchangeable. The only slight distinction is tone: 'somebody' can feel a touch more informal or conversational, while 'someone' is marginally more neutral. Either is correct in almost any sentence.

'Someone' suggests a particular, though unidentified, person and suits positive statements: 'Someone called for you.' 'Anyone' refers to any person at all, with no one in mind, and fits questions and negatives: 'Did anyone call?' or 'I didn't see anyone.' The choice shifts the meaning subtly.

'Someone' is grammatically singular and takes a singular verb: 'Someone is waiting.' However, it is very common and widely accepted to refer back to it with 'they' when the person's gender is unknown, as in 'Someone left their coat.' This neatly avoids the clumsy 'his or her.'

'Someone is knocking at the door,' 'I need someone to help me,' and 'She is someone I truly admire' all use the pronoun. It stands in for a person whose identity is unknown, unimportant, or deliberately left vague in the sentence.