Yellow Card – a penalty card intended as the first and last warning to a player about his or her rule-violating behavior, a second “Yellow Card” violation leads to a “Red Card” 

Yo-Yo Club – a team which is constantly being “Promoted” and “Relegated” between leagues

Youth System – a club’s training program for younger players intended to groom them for eventual advancement to the “First Team” 

Zonal Marking – a defensive scheme in which each defender is assigned a specific area of the field to cover instead of an individual opponent; the opposite of “Man Marking”