Greek word · G878

ἄφρων

aphrōn

foolish

Made from a- ('without') and phrēn ('mind, good sense'). It describes someone who lacks sound practical judgment: senseless, thoughtless, reckless. In Jewish usage it is moral as much as mental. The fool is the person who lives as though God's order did not matter.

Appears 11 times in 10 verses of the Greek New Testament. · Updated November 01, 2026

What it means

ἄφρων, -ον genitive -ονος

(φρήν), [in LXX for כְּסִיל, נָבָל, etc. ;]

without reason, senseless, foolish, expressing "want of mental sanity and sobriety, a reckless and inconsiderate habit of mind" (Hort; cf. MM, see word): Luke 11:40 12:20, Romans 2:20, 1 Corinthians 15:36, 2 Corinthians 11:16 12:6 12:11, 1 Peter 2:15; opposite to φρόνιμος, 2 Corinthians 11:19; to συνιέντες, Ephesians 2:17.†

(AS)

From G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922), via STEPBible.org (CC BY 4.0).

In depth

From the study of Ephesians 5:17

Range of meaning: Made from a- ('without') and phrēn ('mind, good sense'). It describes someone who lacks sound practical judgment: senseless, thoughtless, reckless. In Jewish usage it is moral as much as mental. The fool is the person who lives as though God's order did not matter.
Against the English: English 'foolish' can sound like 'silly' or 'embarrassing'. KJV's 'unwise' sounds like a mild lack of cleverness and blurs it with 'unwise' (asophoi) in verse 15. The Greek word is stronger and has a moral edge: a life that is not steered by sense.
How it drifted: In modern English 'foolish' has weakened toward 'silly' or 'mistaken'. The biblical 'fool' was a moral character type.
Used elsewhere in the period: Common in the Septuagint (the Greek Old Testament) of Proverbs and Psalms for Hebrew kesil and nabal. Psalm 14:1 (LXX 13:1) reads 'the aphrōn said in his heart, There is no God.' Jesus uses it in Luke 12:20 ('Fool! This night…') for the rich man who lived as if he controlled his future. Paul uses it in Romans 2:20 and 1 Corinthians 15:36.

From the study of 2 Corinthians 12:11

Range of meaning: Literally "without phrēn," the faculty of sound judgment. It means senseless, reckless, or foolish in conduct, more than lacking intelligence. In the Jewish wisdom tradition it describes a person who acts without regard for God or for good sense. In Greek moral writing, someone who praises himself is a standard example of the ἄφρων.
Against the English: Every major version has "fool." That is accurate, but a modern reader can hear "I've made an idiot of myself" or "I was stupid." Paul means he has deliberately taken on the role of the senseless boaster ("accept me as a fool," 11:16) and played it to the end.
How it drifted: In English, "fool" now mainly suggests low intelligence or embarrassment. The Greek word is about behavior and judgment, and in this passage it is a costume Paul chose to wear.
Used elsewhere in the period: The LXX (the Greek translation of the Hebrew Scriptures) uses ἄφρων over and over in Proverbs for the Hebrew kesil and nabal, and in Ps 14:1 / 53:1: "the fool has said in his heart, 'There is no God.'" Jesus calls the rich man in his parable "ἄφρων" (Luke 12:20). Paul uses it about the Corinthian questioner in 1 Cor 15:36. Within the Fool's Speech it appears at 11:16 (twice), 11:19, 12:6 and here, and the related noun ἀφροσύνη appears at 11:1, 17, 21. Plutarch's essay On Praising Oneself Inoffensively treats self-praise as offensive behavior that is excused only under certain conditions.

From the study of 1 Corinthians 15:36

Range of meaning: Literally 'without phrēn': without the mind's power of judgment and good sense. So: senseless, thoughtless, imprudent, foolish. The word describes failing to think properly and acting against one's own understanding. It is not mainly about low intelligence, and it is not a word for a jester or clown.
Against the English: BSB and NASB 'You fool!', ESV 'You foolish person!', NIV 'How foolish!', NLT 'What a foolish question!'. In modern English 'You fool!' sounds like a contemptuous personal insult. The Greek is sharp, but it sits within a recognised teaching style in which a speaker scolds an imaginary objector. NLT softens the rebuke by aiming it at the question instead of the questioner.
How it drifted: English 'fool' has shifted toward 'idiot' or 'clown', and many readers also remember Jesus' warning about calling someone 'fool' (Matt 5:22). That warning uses a different word (mōre) in a different setting: contempt for a brother. Paul's word here is the wisdom-literature word for someone who is not thinking straight.
Used elsewhere in the period: The Greek Old Testament (Septuagint) uses aphrōn constantly for the 'fool' of Proverbs and of Psalm 14:1 (LXX 13:1), 'The fool says in his heart, There is no God.' Jesus uses it in Luke 11:40 ('Fools! Did not the one who made the outside…') and in Luke 12:20 for the rich farmer. That farmer is also a man of seed and harvest who does not reckon with death. Paul applies it ironically to himself in 2 Cor 11–12 ('I speak as a fool'). Philosophers' teaching dialogues used similar sharp forms of address to imagined opponents, e.g. 'O man' (Rom 2:1; 9:20) and 'O empty man' (Jas 2:20).

Where it appears

Luke · 2

Luke 11:40 ἄφρονες, Fools!

You fools! Did not the One who made the outside make the inside as well?

Here: A plural address: 'you senseless ones!' This is the wisdom literature's word for people who lack practical moral understanding and live as if God does not see. It is not a jab at their intelligence.
Luke 12:20 ἄφρων, Fool!

But God said to him, ‘You fool! This very night your life will be required of you. Then who will own what you have accumulated?’

Here: Someone who lacks sound practical and moral judgment. In Israel's wisdom tradition this is the person who lives as if God did not matter. It is a verdict, not a playground insult.

Romans · 1

Romans 2:20 ἀφρόνων, of [the] foolish,

an instructor of the foolish, a teacher of infants, because you have in the law the embodiment of knowledge and truth—

Here: People without sound judgment or practical good sense. In the flow of Romans it points to the non-Jewish nations, whom Paul has just described in chapter 1 as having 'darkened' minds and becoming fools.

1 Corinthians · 1

1 Corinthians 15:36 ἄφρων, Fool

You fool! What you sow does not come to life unless it dies.

Here: A sharp form of address to the imagined objector of v.35: 'you're not thinking!' It means someone failing to use the understanding they have, and it says nothing about their worth as a person. A pointed choice in a letter to people who were proud of their wisdom (1 Cor 1–4).

2 Corinthians · 5

2 Corinthians 11:16 ἄφρονα ἄφρονα a fool

I repeat: Let no one take me for a fool. But if you do, then receive me as a fool, so that I too may boast a little.
2 Corinthians 11:19 ἀφρόνων, fools,

For you gladly put up with fools, since you are so wise.
2 Corinthians 12:6 ἄφρων· a fool;

Even if I wanted to boast, I would not be a fool, because I would be speaking the truth. But I refrain, so no one will credit me with more than he sees in me or hears from me,
2 Corinthians 12:11 ἄφρων a fool

I have become a fool, but you drove me to it. In fact, you should have commended me, since I am in no way inferior to those “super-apostles,” even though I am nothing.

Here: Someone without sound judgment. Here it is the role Paul knowingly put on to boast (11:1, 16–17, 21; 12:6). He is not admitting he is stupid. He means that boasting about yourself is senseless behavior, and he has just done it.

Ephesians · 1

Ephesians 5:17 ἄφρονες, foolish,

Therefore do not be foolish, but understand what the Lord’s will is.

Here: Literally 'without phrēn', without sound judgment. It is the fool of Proverbs: someone who lives carelessly and without moral sense, not someone low in intelligence.

1 Peter · 1

1 Peter 2:15 ἀφρόνων of foolish

For it is God’s will that by doing good you should silence the ignorance of foolish men.

Here: "Senseless": people lacking sound judgment. In the Jewish wisdom tradition this is the person who will not reckon with God, not simply someone silly.

Word data: STEPBible.org (CC BY 4.0), main text only.