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)

• nursers
• nursery
• nursery cannon
• nursery class
• nursery classes
• nursery governess
• nursery-governess
• nursery-governesses
• nurserymaid
• nurserymaids
• nurseryman
• nurserymen
• nursery nurse
• nursery nurses
• nursery rhyme
• nursery rhymes
• nursery school
• nursery schools
• nursery slopes
• nursery stakes
• nurses
• nurse shark
• nurse sharks
• nurse-tend
• nurse-tended