| keynote(noun, support, action, idea, base) |
| main point(noun, expression, essence, profit, core) |
| main thing(noun, expression, essence, profit, core) |
| meaning(noun, quality, character, strength, spirit) |
| nexus(noun, support, action, join, point) |
| node(noun, join, point, link, junction) |
| nut to crack(expression, idiom, secret) |
| polestar(noun, emotion, heart, soul, mood) |
| poser(difficulty, question, secret, puzzle, obscurity) |
| predicament(noun, trouble, change, pass, join) |
| principle(noun, support, action, quality, character) |
| purpose(noun, emotion, meaning, mood, temperament) |
| puzzlement(question, secret, puzzle, obscurity, knot) |
| puzzler(difficulty, question, problem, puzzle, mystery) |
| quandary(noun, trouble, change, pass, join) |
| question mark |
| rub |
| secret(noun, trouble, challenge, question, puzzle) |
| sine qua non(noun, expression, idiom, heart, essential) |
| sixty-four-thousand-dollar question(expression, difficulty, question, secret, puzzle) |