"I will call you withing 2 hours" means that you will call anytime starting from this moment but no later than 2 hours after this moment. "I will call you in 2 hours" means that you will call no sooner than 2 hours after this moment. "The work will be ready in 2 hours".

hi Phil, actually both are referring to anything having inside or internal to: 'The culprit is in the city.' 'The culprit is within the city.' Can you figure out the difference? the latter statement indicates that the culprit could be anywhere in the city (in the center or in any point bounded by that city), while the former is trying to say that the culprit is 'inside' the city - which is a general statement to say... seems no difference at all, right? :)

Hi Phil, use 'in' to mean inside eg' I am going in now because it's cold'. 'Within' has 5 shades of meaning. The first definition of within : In the inner or interior part of; inside of; not without; as, within doors. Within 2 Definition: Hence, inside the limits, reach, or influence of; not going outside of; not beyond, overstepping, exceeding, or the like. Within 3 Definition: In the inner part; inwardly; internally. Within 4 Definition: In the house; in doors; as, the master is within. within 5 Definition: on the inside; "within, the car was a mess"