| integral(adjective, important, essential, critical) |
| integrant(fundamental, shorts, undercarriage) |
| intermediacy(root, mainspring) |
| kernel(noun, emotion, heart, soul, mood) |
| key(adjective, important, essential, critical) |
| law(noun, foundation, basic, stipulation, tenet) |
| leonine(adjective, renowned, meritable, noted, highpowered) |
| life-or-death(adjective, important, essential, critical, renowned) |
| life or death(expression, adjective, idiom, renowned, meritable) |
| lifeblood(fundamental, shorts, undercarriage) |
| lionlike(adjective, renowned, meritable, noted, highpowered) |
| main idea(expression, root, mainspring, intermediacy) |
| mainspring(root, intermediacy) |
| meaningful(adjective, important, essential, critical) |
| meat(noun, spirit, heart, basic, bosom) |
| meat-and-potatoes(adjective, important, essential, critical, renowned) |
| meretorious(adjective, renowned, meritable, noted, highpowered) |
| meritable(adjective, renowned, noted, highpowered, bottom-line) |
| mettle(noun, emotion, mood, temperament, core) |
| middle(noun, emotion, heart, soul, mood) |