0 the middle stone in the top of an arch that has a special shape and holds all the other stones in position
1 the most important part of a plan, idea, etc. on which everything else depends
2 the most important part of a plan, idea, etc. on which everything else depends:
In this process, users get immediate information as to frequency, context and usage: three keystones to lexicography.
The keystones are richly carved and the arch soffit is deeply coffered and enriched.
Flagships, umbrellas, and keystones: is single-species management pass' in the e landscape era?
The assumption that "consent" is the source of a government's legitimacy represents a conceptual keystone in liberal theory.
Thus, this sector has been identified as a keystone for agricultural development in these developing nations.
However, those treatments containing high proportions of alfalfa also attracted higher numbers of herbivorous keystone species.
In this paper the concept of keystone plant resources is reviewed using potential candidates proposed in the literature for neotropical forest sites.
Such research should concentrate on the regeneration after fire and the modes of establishment of keystone species.
