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)

• longevities
• longevity
• longevous
• longe whip
• long face
• long-faced
• long faces
• long field
• long fields
• long-firm
• long-firms
• long-hair
• long-haired
• long-hairs
• longhand
• longhands
• long haul
• long-haul
• long hauls
• long-head
• long-headed
• long-headedness
• long-heads
• long home
• long hop