This piece was originally published on Slate .

James Clapper, the director of national intelligence, has been harshly criticized for having misled Congress earlier this year about the scope of the National Security Agency's surveillance activities. The criticism is entirely justified. An equally insidious threat to the integrity of our national debate, however, comes not from officials' outright lies but from the language they use to tell the truth. When it comes to discussing government surveillance, U.S. intelligence officials have been using a vocabulary of misdirection—a language that allows them to say one thing while meaning quite another. The assignment of unconventional meanings to conventional words allows officials to imply that the NSA's activities are narrow and closely supervised, though neither of those things is true. What follows is a lexicon for decoding the true meaning of what NSA officials say.

Surveillance. Every time we pick up the phone, the NSA makes a note of whom we spoke to, when we spoke to him, and for how long—and it's been doing this for seven years. After the call-tracking program was exposed, few people thought twice about attaching the label "surveillance" to it. Government officials, though, have rejected the term , pointing out that this particular program doesn't involve the NSA actually listening to phone calls—just keeping track of them. Their crabbed definition of "surveillance" allows them to claim that the NSA isn't engaged in surveillance even when it quite plainly is.

Read the rest of the NSA Lexicon on Slate .