Associate
Disassociate
Association
Unassociated
Allow
Disallow
Allowance
Allowable
Compete
Competition
Competitor
Competitive(ly)
Enjoy
Enjoyment
Enjoyable
Equip
Equipment
Equipped
Fortune
Misfortune
Unfortunately
Interest
Uninterestingly
Know
Knowledge
Unknowledgeable
Lose
Lost
Loss
Maintain
Maintenance
Medal
Medallist
Medallion
Oppose
Opposition
Opponent
Opposite
Opposing
Practice
Practise
Impractical(ly)
Train
Retrain
Trainer