This is the 244th most frequent Greek word.
λάθος
Mistake.
The word "λάθος" is used here as a noun to denote an error made in performing a calculation.
Έκανα ένα λάθος στον υπολογισμό.
I made a mistake in the calculation.
Here, "λάθος" functions as an adjective, describing the incorrectness of someone's behavior.
Είναι λάθος να μιλάς έτσι στους φίλους σου.
It is wrong to speak to your friends like that.
In this case, "λάθος" is used adverbially to characterize the attribute of the information being incorrect.