a young child or infant, viewed as immature and not yet grown up; also, figuratively, a person who is immature, untaught, or childlike in simplicity
The word pictures the earliest and most helpless stage of life, the infant who cannot yet speak or fend for itself. From that literal picture the New Testament draws a whole range of figurative uses, all turning on the one idea of not being grown up yet.
Most often the figure is a gentle rebuke. Paul and the writer of Hebrews call believers who have stalled "infants" when they should have matured: still on milk rather than solid food, and easily blown about by every new teaching. In these places the word is the opposite of τέλειος, the "mature" or "complete" adult, and that contrast is the whole point.
But the same word can be praise. Jesus thanks the Father for hiding his truth from the wise and clever and revealing it to "little children" (Matthew 11:25): not the immature, but the humble and receptive, who take God at his word as a small child would.
Unlike the neutral παιδίον, which simply names a young child, this word almost always carries that added weight of immaturity or dependence, whether the writer means it kindly, critically, or as a plain fact about an heir who is still under age.
Nuances
Whether Paul wrote νήπιοι ("infants") or the almost identical ἤπιοι ("gentle") in 1 Thessalonians 2:7, since the two words differ by one letter and the preceding word ends in that same letter.
- contestedPaul wrote "infants" (νήπιοι): it has the earliest and most diverse manuscript support and is the harder reading, picturing the apostles as unassuming as small children.; Fee, The First and Second Letters to the Thessalonians (NICNT); Metzger, A Textual Commentary on the Greek New Testament, 2nd ed.
- contestedPaul wrote "gentle" (ἤπιοι): the extra letter arose by accidental doubling from the preceding word, and "gentle" fits the nursing-mother image in the same sentence.; Malherbe, The Letters to the Thessalonians (Anchor Yale Bible)