| fountainhead(cause, quick, source, origin, stem) |
| fundamental(cause, quick, source, origin, stem) |
| germ(cause, source, origin) |
| gravamen(root, mainspring, intermediacy) |
| ground(cause, source, origin) |
| groundwork(cause, quick, source, origin, stem) |
| heart(cause, source, root, origin, mainspring) |
| hotbed(root, mainspring, intermediacy) |
| inception(cause, source, origin) |
| infrastructure(cause, quick, source, origin, stem) |
| intermediacy(root, mainspring) |
| main idea(expression, root, mainspring, intermediacy) |
| midpoint(root, mainspring, intermediacy) |
| motive(cause, source, origin) |
| nave(root, mainspring, intermediacy) |
| nitty gritty(expression, root, mainspring, intermediacy) |
| nub(cause, source, origin) |
| nucleus(cause, source, origin) |
| occasion(cause, source, origin) |
| omphalos(root, mainspring, intermediacy) |