A set of six balls bowled in cricket - is called an 'over'.
balls bowled divided by wickets
highestly9 balls per over has been bowled in one day cricket.
In Australian cricket until 1979 they had 8-ball overs!
There are six legal balls bowled in one over, meaning that their has to be six balls which are not deemed to be no balls or wides.
Overs means number of balls bowled or going to bowl against opposite team.
By illegitimate, I presume you refer to a no-ball or a wide. Under current rules an over contains 6 balls. Some years back, 8-ball overs were used in Australia if nowhere else. For an over to be complete, 6-balls not including a wide or no-ball must be bowled. If an illegitimate ball is bowled, it must be rebowled. The most illegitimate balls bowled in one over was an over bowled by Curtly Ambrose in his final test on Australian soil which contained 9 no-balls - a total of 15 balls.
6 balls constitutes an "over". The length of a game in limited overs cricket is dependent on how many overs are being played - 20, 50 etc. Unlimited is dependent on time.
6 balls in an over English sports, cricket http://en.wikipedia.org/wiki/Over_(cricket)
10 - 0 from 27 balls all bowled. See Guinness Book of records 1996 or 1997 before they removed amateur records.
If there are no extras, then only 30 balls will be bowled. If there are extras, more balls will be bowled depending on the number of extras.