Question: Are defensive and offensive positions similar or different?
About the article "Water polo", section "Defense".

Candidate passages:
In American football and Canadian football, defensive backs (DBs) are the players on the defensive team who take positions somewhat back from the line of scrimmage; they are distinguished from the defensive line players and linebackers, who take positions directly behind or close to the line of scrimmage.
The defensive backs, in turn, generally are classified into several different specialized positions: Safety: *Free Safety - most often the deepest safety *Strong Safety - the bigger more physical safety, much like a small, quicker linebacker Defensive halfback (Canadian football only) Cornerback - which include: *nickel back - the fifth defensive back in some sets, like the Nickel formation *dime back - the sixth defensive back in some sets, like the Dime formation *The seventh defensive back, in the exceedingly rare 'quarter' set **known as a dollar back or a quarter back (not to be confused with the offensive player who throws the ball) The group of defensive backs is known collectively as the secondary.
They most often defend the wide receiver corps; however, at times they may also line up against a tight end or a split out running back.
They are usually the smallest, quickest players on the field. 
Half dollar defenses have eight defensive backs and are very rare and are often used to prevent a Hail Mary pass.
Professional teams may not have enough defensive backs on the roster to play the quarter or half dollar, so wide receivers are sometimes used to fill the extra positions, particularly in late game situations where the receiver's offensive skills can be put to good defensive use. 
The defensive linemen line up in front of the offensive line.
The defensive lineman's responsibility is to prevent the offensive line from opening up running lanes for the running back or to sack the quarterback, depending on whether the play is a passing or running play.
Most of the time, defensive linemen attack the offensive line but in some plays they drop back in pass coverage to confuse the opposite team.
Defensive nose guard: The nose guard ("NG"), also known as a nose tackle ("NT"), lines up across from the center.
Nose guards are among the biggest players on the field and mainly are used to push back the center or the guard to stop a running play or to move the offensive linemen to where the linebackers can rush the quarterback.
Defensive tackle: The defensive tackle ("DT") lines up against the guard or center on the offensive line.
Defensive tackles are generally the biggest and most powerful players on defense; many of them are of the same size as the offensive line.
They tend to be more the "run-stopping" type rather than being good at rushing the quarterback themselves.
Defensive end: Defensive ends ("DE") line up just outside of the offensive tackle.
Defensive ends need to be strong to be able to not be pushed back by the offensive line, yet fast enough to run around the offensive tackle.
There are different types of defensive ends; some are about as strong as DTs and are considered more adept at stopping the run, while others are fast and agile, and are much better at rushing the quarterback than stopping the run.  
In American football, like many other sports, there are many coaches and assistant coaches.
American football includes a head coach, an assistant head coach, an offensive coordinator, a defensive coordinator, a special teams coordinator, offensive and defensive line coaches, coaches for every position, and a strength and conditioning coach, among other positions. 
Described here are positions seen in NDA of Japan, but usually the position Ninja is absent when played in other schools.
On the defensive half, positions include: pole support, barrier, interference, scrum disabler and the ninja.
Offensive positions include: springboard/scrum, pole attackers and general support attacks.