Aha! Both of these nouns describe a moment of clarity, when we intuitively discover the true nature or meaning of something. An insight often appears as something given or provided to us by another person, or by a book, documentary, or article: provides a valuable insight into the poet’s process. Even putting aside the overuse of insight (Thank you for your insights!), an epiphany is an insight on a much grander scale, so much so that many of us are more familiar with it as a literary device. Epiphany suggests a sudden revelation or realization of a truth of great significance to us, usually triggered, sparked, or inspired by something ordinary or commonplace. Typical adjectives used with epiphany are personal, sudden, spiritual, and life-changing. An epiphany is a personal paradigm shift, which changes the way one sees everything.

Both words refer to two or more things coming together to form one entity. Unite, the more familiar term, has a broad range of reference, from two people uniting in marriage to groups uniting to form a single unit with a single purpose. Although unite sometimes refers to actual physical combination of once separate units, it often suggests a figurative becoming as one. Coalesce is more commonly used for literal fusion. It suggests a growing together, intermingling, or blending so that, especially in the sciences, we see it used of liquids, atoms, clouds, dust, coalescing to form a single substance or object. Still, the figurative use of coalesce is the most common, particularly for groups of people: local groups coalescing to form a national movement.

Both words refer to something that is the only one of its kind. Unique, in this sense (it has several), suggests being the only one in existence or the only example of something: As far as we know, every snowflake is unique. Sui generis is a strong synonym for unique in this example. The translation of this phrase borrowed from Latin is “of its own kind.” Sui generis in a strict sense refers to something that does not fit into any existing category and therefore is its own category (and that category’s sole member). The European Union is said to be a sui generis organization. Sui generis often implies something that, to be dealt with, requires a new rule or approach: a sui generis situation, problem, or species. The term is used in law, biology, and other fields: a sui generis species needs its own genus. In less rigorous contexts, you can say someone has a style that is sui generis without fear of repercussions.