flat

Definition

Having no variations in height.

Etymology

From Middle English flat, a borrowing from Old Norse flatr (compare Norwegian and Swedish flat, Danish flad), from Proto-Germanic *flataz, from Proto-Indo-European *pleth₂- (“flat”); akin to Saterland Frisian flot (“smooth”), German Flöz (“a geological layer”), Ancient Greek πλατύς (platús), Latvian plats, Sanskrit प्रथस् (prathas, “extension”). Doublet of plat and pleyt. The noun is from Middle English flat (“level piece of ground, flat edge of a weapon”), from the adjective. The algebraic sense was coined by Serre in a 1956 paper, originally as French plat.

Example Sentences

• "The land around here is flat."
• "a flat roof"
• "The surface of the mirror must be completely flat."