Here are a few of my favourite words that are somewhat formal-sounding, not used particularly often in day-to-day life, and that can really add a sense of poeticism to your English! If you can come up with any interesting sentences using any of these words, then I'd love to hear them. Infinitesimal: extremely small Propensity: the fact that someone is likely to behave in a particular way (e.g. he has a propensity for arriving late) Hubris: an extreme and unreasonable sense of pride and dangerous self-confidence Skulduggery: dishonest and deceitful behaviour Unscrupulous: lacking in any moral principles, conscience, or sense of right and wrong Dichotomy: a difference between two completely opposite things or ideas Conniving: being deceitful and dishonest for one's own advantage