People noticed, and debated its use. That is because, from the childhood schoolyard to the grave, this is a word neither used nor taken lightly. It stands apart from most other terms in the linguistic ballpark of untruths, including “falsehood,” which Chuck Todd, the host of “Meet the Press,” recently used to counter the Trump adviser Kellyanne Conway’s Orwellian phrase, “alternative facts.”

To say that someone has “lied,” an active verb, or has told a “lie,” a more passive, distancing noun, is to say that the person intended to deceive. In addition, Mr. Nunberg said, “a certain moral opprobrium attaches to it, a reprehensibility of motive.”

The question of intent has informed National Public Radio’s approach to covering Mr. Trump’s many disputable claims: that he saw thousands of people in Jersey City cheering as the World Trade Center collapsed on Sept. 11, for example, or that the news media had made up a feud between him and the country’s intelligence agencies, despite his own tweets likening those agencies to Nazi Germany.

On NPR’s “Morning Edition” on Wednesday, Mary Louise Kelly explained that she had looked up the definition of “lie” in the Oxford English Dictionary. “A false statement made with intent to deceive,” Ms. Kelly said. “Intent being the key word there. Without the ability to peer into Donald Trump’s head, I can’t tell you what his intent was. I can tell you what he said and how that squares, or doesn’t, with facts.”

Michael Oreskes, NPR’s senior president for news, supported the decision. In an article on the NPR website, Mr. Oreskes said that “the minute you start branding things with a word like ‘lie,’ you push people away from you.” The inherent risk, he suggested, was that news organizations would be seen as taking sides.

Editors at The Times also consulted dictionaries. And they had some prior experience with the matter, having approved the use of the L word once before in reference to Mr. Trump.

In September, when he grandly announced the findings of a yearslong so-called investigation into what nearly everyone else never doubted — “President Obama was born in the United States, period” — The Times published a Page 1 article with the headline “Trump Gives Up a Lie but Refuses to Repent.”