Stranger in a Strange Land
"Yes, Jubal. You—" Smith stopped, looked embarrassed. "I again have not words. I will read and read and read, until I find words. Then I will teach my brother" (12.214).
[I]t was not possible to separate in the Martian tongue the human concepts: "religion," "philosophy," and "science"—and, since Mike thought in Martian, it was not possible for him to tell them apart. (14.104)
"You need to think in Martian to grok the word 'grok.'" (21.62)