The most essential part; the main idea or substance (of a longer or more complicated matter); the crux of a matter; the pith.
To summarize, to extract and present the most important parts of.
A central cohesive source of stability and security; a person or thing that is critical to a system or organisation.
A pin inserted through holes at the end of an axle or shaft, so as to secure a wheel or shaft-mounted device.
To adopt as, or serve as, a central cohesive source of stability and security.