The essential element (needed to reach the principal goal or objective); the overall purpose.
The essential or vital part; force; energy; importance.
The spinal cord; the marrow.
The soft, spongy substance in the center of the stems of many plants and trees.
The albedo of a citrus fruit.
The spongy interior substance of a feather or horn.
One divided by pi.
Power, strength, might.
The ordinal form of the number pi.
To extract the pith from (a plant stem or tree).
To kill (especially cattle or laboratory animals) by cutting or piercing the spinal cord.