Abarim Publications' online Biblical Greek Dictionary
The very common adjective καλος (kalos) means good, or in the elaborate reflection of Spiros Zodhiates: "Constitutionally good without necessarily being benevolent; expresses beauty as a harmonious completeness, balance, proportion" (The Complete Wordstudy Dictionary, New Testament).
The difficult concept of goodness merits three solid columns of flowery contemplation in Spiros' dictionary, but Jesus said that only God is good (Mark 10:18, Luke 18:19), and that's probably a great place to start. Add to this that God is love, just, perpetual, productive, a shelter, and the ultimate objective of all evolution (that is to say: nature must eventually either die off or become a unified creature that is compatible with the Creator the way a bride is to her husband), and we may conclude in precisely that practical sense: goodness is godliness — goodness is whatever is lovely, just, perpetual, productive, sheltering and preservative.
Our adjective comes with a surprisingly small number of derivations:
- Together with the noun ελαια (elaia), meaning olive: the adjective καλλιελαιος (kallielaios), denoting a cultivated olive tree (Romans 11:24 only), as opposed to αγριελαιος (agrielaios), the wild olive tree.
- The comparative καλλιον (kallion), meaning better (Acts 25:10).
- Together with the noun διδασκαλος (didaskalos), meaning teacher: the adjective καλοδιδασκαλος (kalodidaskalos), meaning teacher of good things. This word appears to be coined by Paul. It occurs only in Titus 2:3 and not in any other Greek writing.
- Together with the verb ποιεω (poieo), meaning to make, form, cause or do: the verb καλοποιεω (kalopoieo), meaning to do good (2 Thessalonians 3:13).
- The adverb καλως (kalos), meaning well, right or justly (Matthew 15:7, Luke 6:26, John 18:23).