linchpin /linchˈ or linshˈpin/

1. A pin used to keep a wheel on its axle
2. A person or thing essential to a plan, organization, etc (figurative)

• hailstorm
• hailstorms
• hail the dules
• haily
• hain
• hainch
• hained
• haining
• hainings
• hains
• haique
• haiques
• hair
• hair-ball
• hair-balls
• hairband
• hairbands
• hairbell
• hair-brained
• hairbreadth
• hairbrush
• hairbrushes
• haircloth
• haircloths
• haircut