When referring to the possessive, I didnít know that its and oneís are spelt in a different way, its without the apostrophe and oneís with the apostrophe. Please explain more.
Its is a possessive like my, your, his, her, our and their and you are quite right, it is very important not to insert an apostrophe when using it in this way.
Its is the neutral equivalent of his and her. Study the following:
* 'Every country has its own customs and traditions.'
* 'It was a Manx cat and its tail was therefore very short.'
* 'Its coat was very thick.'
* 'Mary had a little lamb. Its fleece was [as] white as snow. And everywhere that Mary went, the lamb was sure to go.' (Trad. English nursery rhyme)
It is important not to confuse its with itís.
Itís is the contracted form of it is or it has and usage is, of course, completely different. Study the following four examples.
See if you can work out in which of them itís is the contracted form of it is and in which of them itís is the contracted form of it has.
* 'Whatís the time?' 'Itís a quarter to nine.' 'Itís time for you to go to bed!'
* 'Whoís that over there?' 'I donít believe it. Itís Prince William!'
* 'Howís the condition of the man injured in the car crash?' 'Itís improving all the time.'
* 'Have you seen my watch? Itís disappeared from the bathroom. Itís got a bright yellow strap.'
(Itís only in the fourth example above that itís is the contracted form of it has.)
Oneís is also a possessive determiner like your and is used to talk about people in general.
Oneís is more formal than your. Compare the following:
* 'A home of oneís own is what most people aspire to.'
* 'You always want the best for your children Ė thatís only natural.'
Note that one and you are similarly formal/informal:
* 'You canít learn a foreign language in four or six weeks. Itís impossible.'
* 'If one wishes to perfect oneís English, one has only to go to a country where it is spoken.
Finally note that one and ones (this time without the apostrophe) are sometimes used as substitute words, i.e. we use them rather than repeating countable nouns.
In this aspect, oneís is also possible when it is the contracted form of one is. Study the following:
* 'Could I try on those shoes?' 'Which ones?' 'The ones in the window at the front on the left.'
* 'There are so many children in this photo. Which one is your daughter?' 'The one in the blue dress.'
* 'I really like these sweaters, but do you have any other sizes? This oneís too small and that oneís too big.