Plain as day
Meaning
Extremely clear and obvious, leaving no room for misunderstanding.
Origin
The phrase "plain as day" leans on an ancient human intuition: daylight illuminates everything, making it unmistakable. While "plain" itself has described clarity for centuries—from simple language to unobstructed views—marrying it with "as day" adds a vivid, almost primal emphasis. The natural, undeniable clarity of a bright day provides the perfect metaphor for something so obvious it requires no further explanation, essentially saying "it's as clear and evident as the sun shining at noon." This simple, undeniable comparison solidified the phrase in the English lexicon by the 19th century, remaining a go-to for anything truly straightforward.
Examples
- The instructions for assembling the bookshelf were plain as day; even a child could follow them.
- After she explained her reasoning, the solution to the complex problem became plain as day to everyone in the room.