To know 50% of the words in the GNT, you need to know the 27 most common ones.
The 200 most common words cover just about 75% of the GNT.
The 311 words use 50 or more times cover almost 80% of the GNT.
Greek New Testament Vocabulary Lists. Includes 311 words in Vocabulary Usage Percent List and Vocabulary.50plus.alphabeta.
Greek-English word-list containing about 1000 most common Greek words, so arranged as to be most easily learned and remembered. Published 1893.