Approximate / Exact 
Approximate / Exact
1. Words meaning approximately

approximately 
about 
roughly approximately - used especially when you are trying to give someone
a general idea of the size, number, or amount of something:
 The two countries are roughly the same size.
 The amount of  is roughly equivalent to .(=it contains about the same amount)

(somewhere / something) in the region of approximately. Used with very large 
numbers or amounts:
circa	used before a year, usually one  that is long time ago, to say that 
something happened near that time, but perhaps not exactly in that year:
 The house dates from circa 1600.
or more
10 years / 20% / 100 kilos etc or more used when the total may be a lot more,
and you want to emphasize that this is a large amount: 
 It can take 6 months or more to get a visa.


2. Words meaning exactly

exactly 
to be exact used when you are giving a more exact figure or amount. 
To be exact is used at the end of the sentence: 

precisely a word meaning exactly, used when you  want  to emphasize what 
you are saying:
 The meeting began on time, at precisely eight o'clock. 
right in the middle of / next to / in front of etc used when you are emphasizing 
that something is in a particular position:
 The arrow was right in the middle of the target. 
directly in front of / behind / under etc exactly in a particular position:

 It was a small house, directly behind the church.
 A statue stood directly below the stained-glass window.
