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)

• part
• partake
• partaken
• partaker
• partakers
• partakes
• partaking
• partakings
• partan
• part and parcel
• partans
• part brass rags
• part company
• parted
• partenariat
• parter
• parterre
• parterres
• parters
• part-ex
• part-exchange
• part-exchanges
• parthenocarpic
• parthenocarpies
• parthenocarpy