Easy to see through, like clear glass, or easy to understand and not secretive.
From Latin *transparens* “showing through,” from *trans-* “through” + *parere* “to appear.” It came into English in the late Middle Ages, first for physical clarity and then for clear explanations or honest behavior.
Calling a lie “transparent” is a clever insult: it means the trick is so obvious you can see straight through it. School windows and simple explanations are both praised for being transparent, even though one is glass and the other is language.
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