Luk 7:9 I say unto you, I have not found so great faith, no, not in Israel.
I'm telling you. not, however, within Israel, so great a trust have I discovered
This line is spoken after the centurion says he isn't worthy to have Christ come to his house. This is an interesting verse to compare to the Matthew version (Mat 8:10) because this is unlikely to be something Jesus said twice. Here, the phrase has been shortened, but the keywords are all the same. The only other difference is that in Matthew, the "in Israel" phrase describes the faith. Here, however, it comes earlier in the sentence. Again, both verses are made to look more the same in translation than they are in Greek.
The Matthew verse started with the "verily" phrase (discussed in detail in this article.) Luke drops the "verily" part of the phrase here and throughout his Gospel, keeping the "I'm telling you" part of it.
The term used for "I_found" is the source of our word, "heuristic," meaning enabling a person to find out something for themselves. It means "find out" and "discover."
The Greek word translated as "not" here is a word combining the negative with the word usually translated as "but" or "however" so "but no" or "no, however." In Matthew, this is a slightly longer word meaning "no one". It was introduced by a proposition that was also removed.
"So much" is a compound adjective that means literally "that which (or who) has to such a degree." This is an uncommon word.
The term translated as "faith" means having confidence or trust in people and especially their words. It did not have the sense of religious belief that the word "faith" has in English today.
There is no second negative here "no, not", much less a double one.
The "in Israel" phrase comes earlier in this verse. It appears more toward the end in the Matthew version.
The word translated as "in" also means "within" or "among." It indicates being within a given area or group. However, the phrase having "faith in" something has a special meaning in English which this word doesn't have in Greek.
The word translated as "Israel" comes from the Hebrew, not the Greek. It refers both to the nation and the people.
Λέγω (1st sg pres ind act) "I tell" is from llego means "pick up", "choose for oneself", "pick out," and "count," "recount", "tell over", "say", "speak", "teach", "mean", "boast of", "tell of", "recite," "nominate," and "command."
τοσαύτην [uncommon](adj sg fem acc) "So great" is from tosoutos, , which means "so much", "thus much", "so far", "so large", and "so tall".
πίστιν (noun sg fem acc) "Faith" is from pistis, which means "confidence", "assurance", "trustworthiness", "credit", "a trust", "that which give confidence," and, as a character trait, "faithfulness."