Abarim Publications' online Biblical Greek Dictionary
The noun καρπος (karpos) means fruit, but has a slightly broader compass than the word fruit does in English. It derives from a very old root that also gave rise to our English words carpet, excerpt and the verbal element "carp" in words such as carpology (the biology of fruits and seeds) and mericarp (a particular portion of a fruit). Our noun also corresponds to the Latin verb carpo, from whence we have the familiar aphorism carpe diem, or pluck the day.
The ultimate meaning of the word καρπος (karpos) does not appear to emphasize the mere production of fruits ex nihilo, but rather the return on an investment (namely seeds and labor). In Greek the word for wrist is also καρπος (karpos), and although it is probably a whole different word, it was probably derived from a root that means to turn around (Liddell and Scott, An Intermediate Greek-English Lexicon).
In the Bible our noun καρπος (karpos) describes the fruit of trees and plants (Matthew 3:10, Luke 12:17, John 12:24) but also the harvest of a field (2 Timothy 2:6). Our word may describe the whole produce of a project such as a vineyard (Matthew 21:41) and even one's children (Luke 1:42, Acts 2:30).
Dictionaries will state that the latter usage and the following are metaphors, but that's an auto-centric mistake. Our word denotes anything that comes about after an initial investment and subsequent effort (Romans 1:13, 7:4), and that includes apples, corn, children and: deeds or works (Matthew 3:8, Luke 3:8), results or effects (hence the "fruit of the Spirit": Galatians 5:22, Ephesians 5:9, but also see Romans 15:28, Hebrews 12:11 and James 3:17), and verbal praise and thanks (Hebrews 13:15).
As such, in many contexts a more proper translation of our word would be "yield" (hence the "yield" of the Spirit).
From our noun derive:
- Together with the particle of negation α (a), meaning without: the adjective ακαρπος (akarpos), meaning unfruitful (Jude 1:12) or producing unprofitable or bad fruits (1 Corinthians 14:14, Ephesians 5:11).
- Together with the verb φερω (phero), meaning to bring: the adjective καρποφορος (karpophoros), meaning fruit-bringing (Acts 14:17 only). From this adjective comes:
- The verb καρποφορεω (karpophoreo), meaning to be fruit-bringing, to be fruitful (Matthew 13:23, Mark 4:28, Colossians 1:6-10).