The Diamond is The Perfection of Wisdom in 300 Lines.
It is often taught within Buddhism that the shorter Prajnaparamita sutras are distillations of the longer ones and that the brief and highly distilled Diamond and Heart sutras were written last.
The sutra's title in Sanskrit, Vajracchedika Prajnaparamita Sutra, could be very roughly translated as the "diamond-cutting perfection of wisdom sutra." Thich Nhat Hanh says the title means "the diamond that cuts through afflictions, ignorance, illusion, or delusion." It is also sometimes called the Diamond Cutter Sutra, or the Vajra Sutra.
The Diamond is part a large canon of early Mahayana sutras called the Prajnaparamita Sutras.
But many scholars suspect the shorter sutras are the older ones, and the longer sutras are elaborations.