Mar 10:42 You know that they which are accounted to rule over the Gentiles exercise lordship over them; and their great ones exercise authority upon them.
Alternative: You see that those imagined to be the nation's foremost lord over them and their strong have power over them.
This verse has a wealth of wordplay and subtle meaning in the Greek that is lost in English translation. Verses such as this are strong indications that Jesus taught in Greek because this wordplay simply doesn't work in Aramaic. See if you think that this could have been the invention of the translators when it fits so well with the next verse.
First, the word rather clumsily translated "are accounted" really indicates a false seeming or imagining. So Christ says starts be saying that those who appear to be the rulers are not necessarily so.
Next, the word translated as "to rule" (archo), which primarily means "to be first." It creates a contrast with the next verse about the last being first.
Finally, the two words translated as "exercise lordship" and "exercise authority" both begin with the word that means "down" (kata), carrying the idea being above and looking down on others. In English, we say that someone "rules over" others, but in Greek, these two words carry the idea of "ruling down" and "using power down" on others. These particular words are only used here and in the corresponding verse in Matthew. Again, the choice of these particular words is a bit too perfect to be simple translation. There are many words that mean rule in Greek that don't begin with kata, but because these do, they fits wonderfully with the following verses about real leaders being beneath others rather than over them.
"You know" is from eidon (eidon), which means "to see", "to perceive", "to behold", "to experience", "to look", "to see mentally", "to examine", "to investigate", "to see with the mind's eye," and "to know how."