Determining rookie status:
A player shall be considered a rookie unless, during a previous season or
seasons, he has (a) exceeded 130 at-bats or 50 innings pitched in the Major
Leagues; or (b) accumulated more than 45 days on the active roster of a Major
League club or clubs during the period of 25-player limit (excluding time in
the military service and time on the disabled list).

Waivers:
A waiver is a permission granted to a Club that desires to assign or release
one of its players. There are basically two types of waivers -- waivers for
the assignment of a player and waivers for the unconditional release of a
player. In both cases, waivers are granted only after all the other Major
League Clubs have been given an opportunity to claim the player and none has
done so. With regard to assignment waivers, permission is granted for a
specific period of time. With unconditional release waivers, once permission
is granted the player is a free agent.

The 40-man roster:
A Club's 40-man roster is a list of all the players currently reserved by a
Club at the Major League level. The Major League Rules permit each Club to
reserve a maximum of 40 players (excluding players on the 60-day disabled
list) at any one time. From September 1 through the end of the season the
entire 40-man roster is eligible to play for the Club at the Major League
level. From Opening Day through August 31, however, a Club may use only 25 of
its 40 players in the Majors.

Determining player performance streaks:
Consecutive Hitting Streaks: A consecutive hitting streak shall not be
terminated if the plate appearance results in a base on balls, hit batsman,
defensive interference or a sacrifice bunt. A sacrifice fly shall terminate
the streak.

Consecutive-Game Hitting Streaks: A consecutive-game hitting streak shall not
be terminated if all the player's plate appearances (one or more) results in
a base on balls, hit batsman, defensive interference or a sacrifice bunt. The
streak shall terminate if the player has a sacrifice fly and no hit. The
player's individual consecutive-game hitting streak shall be determined by
the consecutive games in which the player appears and is not determined by
his club's games.

Consecutive Playing Streak: A consecutive-game playing streak shall be
extended if the player plays one half-inning on defense, or if he completes a
time at bat by reaching base or being put out. A pinch-running appearance
only shall not extend the streak. If an umpire ejects a player from a game
before he can comply with the requirements of this rule, his streak shall
continue.

Suspended Games: For the purpose of this rule, all performances in the
completion of a suspended game shall be considered as occurring on the
original date of the game.

Saves:
Rule 10.20 in the Official Rule Book states:
Credit a pitcher with a save when he meets all three of the following
conditions:
(1) He is the finishing pitcher in a game won by his club; and
(2) He is not the winning pitcher; and
(3) He qualifies under one of the following conditions:
- (a) He enters the game with a lead of no more than three runs and pitches
for at least one inning; or
- (b) He enters the game, regardless of the count, with the potential tying
run either on base, or at bat, or on deck (that is, the potential tying run
is either already on base or is one of the first two batsmen he faces; or
- (c) He pitches effectively for at least three innings. No more than one
save may be credited in each game.

The "Hold":
The hold is not an official statistic, but it was created as a way to credit
middle relief pitchers for a job well done. Starting pitchers get wins, and
closers -- the relief pitchers who come in at the end of the game -- get
saves, but the guys who pitch in between the two rarely get either statistic.
So what's the most important thing one of these middle relievers can do?
"Hold" a lead. If a reliever comes into a game to protect a lead, gets at
least one out and leaves without giving up that lead, he gets a hold. But you
can't get a save and a hold at the same time.

The Designated Hitter rule:
A hitter may be designated to bat for the starting pitcher and all subsequent
pitchers in any game without otherwise affecting the status of the pitcher(s)
in the game. A Designated Hitter for the pitcher must be selected prior to
the game and must be included in the lineup cards presented to the
Umpire-in-Chief.

The Designated Hitter named in the starting lineup must come to bat at least
one time, unless the opposing club changes pitchers. It is not mandatory that
a club designate a hitter for the pitcher, but failure to do so prior to the
game precludes the use of a Designated Hitter for that game.

Pinch hitters for a Designated Hitter may be used. Any substitute hitter for
a Designated Hitter himself becomes a Designated Hitter. A replaced
Designated Hitter shall not re-enter the game in any capacity. The Designated
Hitter may be used defensively, continuing to bat in the same position in the
batting order, but the pitcher must then bat in the place of the substituted
defensive player, unless more than one substitution is made, and the manager
then must designate their spots in the batting order.

A runner may be substituted for the Designated Hitter and the runner assumes
the role of the Designated Hitter.

A Designated Hitter is "locked" into the batting order. No multiple
substitutions may be made that will alter the batting rotation of the
Designated Hitter.

Once the game pitcher is switched from the mound to a defensive position this
move shall terminate the DH role for the remainder of the game. Once a
pinch-hitter bats for any player in the batting order and then enters the
game to pitch, this move shall terminate the Designated Hitter role for the
remainder of the game.

Once a Designated Hitter assumes a defensive position this move shall
terminate the Designated Hitter role for the remainder of the game.

Perfect games and No-hitters:
An official perfect game occurs when a pitcher (or pitchers) retires each
batter on the opposing team during the entire course of a game, which
consists of at least nine innings. In a perfect game, no batter reaches any
base during the course of the game.

An official no-hit game occurs when a pitcher (or pitchers) allows no hits
during the entire course of a game, which consists of at least nine innings.
In a no-hit game, a batter may reach base via a walk, an error, a hit by
pitch, a passed ball or wild pitch on strike three, or catcher's
interference.