Notes:

• The word over, as applied to a set of six deliveries in cricket, derives from the umpire's call of 'over' when those six balls have been bowled to signify that the set is complete.
• The six balls of an over must be legal deliveries; in other words, they cannot be wides or no balls. If an illegal delivery is bowled, the bowler must repeat that delivery. An over can therefore sometimes require seven, eight, or more deliveries (legal + illegal) to be completed.

• A bowler may not bowl consecutive overs. The common practice among captains is to have two bowlers alternate overs from each end of the pitch until they become tired or are deemed ineffective.
• In Test and first-class cricket, the number of overs in a team's innings is indefinite. The number of overs to be bowled in a single day's play is usually expected to be at least 90, a figure which can however be reduced by the umpires as a result of rain or poor light. Umpires offer the bowling team the opportunity to use a new cricket ball after it has bowled 80 overs.
• In one day and Twenty20 cricket, the number of overs in a team's innings is limited. As a result, the number of overs that a single bowler may bowl is also limited to one-fifth of the total allotment for the innings.
• An over in which no runs are scored off the bat and no illegitimate deliveries are bowled is called a 'maiden' and noted in the bowler's overall figures on the scorecard.

Exceptions:

• If a bowler is injured partway through an over and cannot continue bowling, another player from the fielding team will complete the over by bowling the remainder of the six balls. The same situation applies if a bowler is removed from the bowling crease by the umpires for bowling dangerously.

• If the batting team is bowled out partway through an over, or cannot continue its innings, the bowler ends with an incomplete over. A bowler who had bowled eight overs and two balls when the innings ended would be noted on the scorecard to have bowled 8.2 overs.

Examples:

• The best overs showcase technical ability and tactical acumen. During the 1981 Test series between West Indies and England, Michael Holding's opening over to England's Geoff Boycott — a batsman renowned for his defensive technique — went down in history as one of the greatest ever bowled. Holding bowled at high pace and tested different lines, almost dismissing Boycott in the slips, before aiming his final ball at off stump. He sent it cartwheeling out of the ground. Boycott was gone, and West Indies' dominance of that cricket era was further cemented.
• Holding's West Indies colleague Curtly Ambrose, also among the finest fast bowlers to grace the game, managed to send down a 17-ball over against Australia in 1997 as he repeatedly bowled no balls. When Ambrose finally completed the over, 13 minutes after it started, he raised his arms aloft in mock appreciation of the crowd's applause.
• It probably wasn't Shane Warne's greatest over, which is what the video title would have you believe, but this Warne over to New Zealand's Craig McMillan showcased the great legspinner's talents and tactical brilliance. Note how Warne sizes up McMillan's defensive mindset, not to mention his confident swagger around the pitch, before going in for the kill.
• Overs are not all about bowlers. In Australia's Big Bash League, West Indies batsman Chris Gayle smashed 32 runs off one over by hitting four sixes and two fours.