Very often we talk about people or things without knowing exactly who or what they are. Your phone rings and a voice you do not know leaves a message. You come home and the kitchen smells different. For these moments English uses indefinite pronouns: someone, anyone, everyone, no one, something, anything, everything, nothing. They let you speak naturally about the unknown: 'Someone left a message', 'Something smells good.'

Choosing between the some- words and the any- words is the tricky part. If you say 'Anyone left a message', the sentence fails, because any- does not fit a normal positive statement. Learning the small pattern behind some, any, every, and no will fix dozens of everyday sentences at once — offers, questions, complaints, and stories all use these words.

First, learn the family table. For people: someone/somebody, anyone/anybody, everyone/everybody, no one/nobody. For things: something, anything, everything, nothing. The -one and -body forms mean the same: someone = somebody. All of these words are grammatically singular, so they take a singular verb: 'Everyone is here', 'Nothing was missing.'

Now the core pattern. Use the some- words in positive statements about an unknown person or thing: 'Someone is at the door', 'I bought something for you.' Use the any- words in questions and negatives: 'Is anyone home?', 'I didn't buy anything.' Think of it this way: some- says 'this exists, but I don't know its name'; any- keeps the door open — maybe yes, maybe no.

There are two useful exceptions. First, offers and requests often use some- even in question form, because we expect a yes: 'Would you like something to drink?', 'Can I ask you something?' Second, any- can appear in positive sentences with the special meaning 'it does not matter which': 'Anyone can learn this', 'Call me anytime.'

The no- words (no one, nobody, nothing) carry the negative inside themselves, so the verb stays positive: 'Nobody came to the meeting', 'Nothing works.' English allows only one negative per idea. So you must choose: 'I saw nothing' or 'I didn't see anything' — both are correct and mean the same. But 'I didn't see nothing' doubles the negative and is wrong in standard English.

Finally, the every- words mean all people or all things, but grammatically they act singular: 'Everything is ready', 'Everyone knows the answer.' When you refer back to everyone, everyday English often uses they: 'Everyone finished, and they went home.' That is natural and fine in conversation.

1. 1. Someone parked a red car in front of our gate.

   A positive statement about an unknown person uses someone.

2. 2. Is there anything good on the menu tonight?

   A real open question uses anything, not something.

3. 3. I knocked twice, but no one answered the door.

   No one carries the negative, so the verb answered stays positive.

4. 4. Everyone in my class has a bus card.

   Everyone is singular, so the verb is has, not have.

5. 5. We didn't buy anything at the market yesterday.

   In a negative sentence with didn't, use anything, not something.

6. 6. Would you like something sweet with your tea?

   An offer expects a yes, so something is natural in this question.

7. 7. There is nothing in the fridge, so let's order pizza.

   Nothing makes the sentence negative by itself; no extra 'not' is needed.

8. 8. Did anyone call while I was in the shower?

   Open question about people: anyone fits, someone would sound sure.

9. 9. Anybody can join the free yoga class on Saturdays.

   Any- in a positive sentence means it does not matter who.

10. 10. Something is wrong with my laptop; the screen is black.

    You know a problem exists but not what it is, so something fits.

11. 11. Everything in this shop costs under ten dollars.

    Everything covers all the things but still takes a singular verb.

12. 12. She said nothing about the test results at dinner.

    Said nothing equals didn't say anything — one negative, same meaning.

13. 13. If anyone asks, tell them I will be back at noon.

    After if, anyone is common; they refers back to that person naturally.

14. 14. Nobody wants to work outside in this heavy rain.

    Nobody is singular and negative, and wants keeps the -s ending.

The first mistake is using an any- word in a plain positive statement, like the error 'Anyone left a message.' Wrong: 'Anyone left a message.' Right: 'Someone left a message.' A normal statement about a real, existing (but unknown) person needs some-. Save any- for questions, negatives, if-sentences, and the special meaning 'no matter which'.

The second mistake is the double negative. Learners combine not with a no- word: 'I don't know nothing about it', 'She didn't see no one.' Wrong: 'I don't know nothing.' Right: 'I don't know anything' or 'I know nothing.' Pick one negative and let it do all the work; two negatives in one clause is not standard English.

The third mistake is treating every- and no- words as plural: 'Everyone are happy', 'Nobody know the answer.' Wrong: 'Everyone are happy.' Right: 'Everyone is happy.' Even though everyone points to many people, the word itself is singular, so the verb takes the singular form: everyone is, everybody has, nobody knows, everything looks.

• Positive statement about an unknown: use some- (someone, something).
• Questions and negatives: switch to any- (anyone, anything).
• Offers and requests keep some-: 'Would you like something?'
• No- words already say no — never add another 'not' in the same clause.
• Everyone, everything, nobody, and someone all take singular verbs: everyone is, nobody knows.
• Any- in a positive sentence means 'it doesn't matter which': anyone can come.