The DL or Disabled List.
how many players get injured in a year in professional football
'Waived injured' means the team is releasing the player but the player is injured. The team is responsible to pay the player until his injury has healed. This is usually done by reaching an agreement for a specific amount of money, called an injury settlement. Other teams are allowed to pick up players on the waived injured list but they are forewarned that the player is not in condition to play. Sometimes, if a player on the waived injured list is not selected by another team, the team will retain the player and place him on its injured reserve list.
A baseball lineup is the list of players that will participate in a game.
Injured Reserve: Players that are injured and will be unavailable to play for a lengthy amount of time are placed on this list so that a team may bring in other players as replacements.
Yes, but only in case of injury. According to MLB Rule 40A: "A player must be on his club's active big league roster or disabled list (or bereavement list, suspended list, or military list) on August 31 in order to be eligible for post-season play." However, there are rules that allow for players that were called up in September to replace players that are injured during the playoffs and placed on the disabled list. In these cases, the replacement player must have been on the team's 40 man roster and must play the same position as the injured player.
Rosters are the list of eligible players who can play for a team.