scales

The word “scales” means a device with two pans used to measure and compare weight. In plain terms, the plural form used for a weighing instrument, especially the classic two-pan balance.

“Scales” is pronounced skaylz (/skeɪlz/ in IPA).

Here is “scales” used in a sentence: “She weighed the flour on the kitchen scales.”

“Scales” is a noun.

The word “scales” comes from Old Norse. From Old Norse skáli, "bowl, hut" — referring to the pans of a balance.

“Scales” is a fairly common word in modern English.

British English normally uses the plural: a set of kitchen scales, standing on the bathroom scales. American English usually treats the device as singular: a kitchen scale, a bathroom scale. Both names refer to the same instrument.

The traditional weighing device had two pans hanging from a beam, and each pan was called a scale. The plural scales originally referred to that pair of pans, and the usage survived even after single-platform designs replaced the two-pan type.

Both weigh things, and the classic two-pan device can be called either. Balance is the more technical term, used in laboratories for precise instruments that compare a sample against known weights, while scales is the everyday household and shop word.