nodus

/ˈnoʊdəs/
noun
  1. A difficult or complicated situation; a problem or knotty point.
    • The plot of the mystery novel revolves around a nodus that the detective must solve.
    • She faced a moral nodus when she had to choose between telling the truth and protecting her friend.
    • The negotiators finally untangled the nodus that had stalled the peace talks.
  2. A knot or swelling, especially in a biological or anatomical context.
    • In the insect's wing, the nodus is a thickened point that helps with flight stability.
    • The botanist noted a small nodus on the stem where the leaf had once attached.
    • The surgeon carefully removed the nodus from the patient's thyroid gland.