The prepositions ‘in’ and ‘within’ are often interchangeably; but there is a subtle difference and the nuances are often not understood. In the extract below, we see ‘within’ being used incorrectly a number of times: ‘within’ suggests being inside of or enclosed in something; ‘in’ suggests related to or present. But these broad meanings are not definitive or exclusive and exposure to common English phraseology is needed in order to determine when to use ‘within’ and when to use ‘in’ – simply because something doesn’t ‘sound right’. This relates not only to the sound the words make, but also to collocations and what word fits more naturally in a sentence. And this is not something that can be taught in a few months or years of second-language instruction: it is something that is ‘absorbed’ over years and years of hearing and reading good quality first-language English. This is why prepositions are often problematic for many people.