invaluable /in-valˈū(-ə)-bl/

1. That cannot have a value set upon it
2. Priceless

• First Book of Discipline
• first-born
• first cab off the rank
• first catch your hare
• first cause
• first chop
• first-class
• first-class mail
• first-class post
• first cousin
• first cousin once removed
• first-day
• first-day cover
• first-day covers
• hexaëmeron
• hexed
• hexene
• hexenes
• hexes
• hexing
• hexings
• hexobarbitone sodium
• hexose
• hexoses
• hexyl