谎言(huǎng yán) - lie, falsehood in Mandarin

谎言 (huǎng yán) is a lie as a thing: the falsehood itself, the sentence somebody uttered. It is a noun and only a noun, and it sits comfortably in written and dramatic language.

To lie as an action you need 撒谎 (sā huǎng), which is a separable verb-object pair. English lets "lie" be both noun and verb; Chinese keeps them apart, so 他撒谎 is he lied and 他的谎言 is his lie. Trying to use 谎言 as a verb is the mistake to avoid.

The white lie has its own phrase, 善意的谎言 (shàn yì de huǎng yán), literally a lie with good intentions. It comes up often enough in conversation about family that it is worth banking as a chunk.