to have the strength or power for something: to be strong enough, be able, or prevail
TranslatabilityPartialCertaintySettled
At its root this word is about having real strength or force, not merely permission or bare possibility. Most often it describes a person who is (or is not) strong enough to get something done: to finish a building, cast out a spirit, keep watch one more hour, or haul in a heavy net. That is why it so often appears in the negative, marking the point where human strength runs out.
The same core stretches in a few directions depending on what has the strength. Of a body it means being well and robust, as when Jesus says the healthy have no need of a doctor. Of a thing rather than a person it means carrying force or weight: salt that is good for nothing, a legal will that only takes effect once someone has died, or a righteous person's prayer that accomplishes a great deal. And in a contest it means to win out or overpower an opponent.
All of these are one idea seen from different angles: strength that is actually up to the task. When Paul says he can do all things through the one who strengthens him, he is claiming exactly this power, and naming its source outside himself.
used of winning out over active opposition, whether a man overpowering others or an enemy failing to gain groundAct 19:16Rev 12:8
Both
both describe strength that succeeds in a contest or against resistanceAct 19:16
Only prevail
the English word "prevail" always implies a struggle to overcome, but this Greek word only carries that force in some settings and elsewhere just means "be able" or "be effective"
used of a thing rather than a person carrying real force or weight: circumcision counting for nothing, a prayer accomplishing muchGal 5:6Jas 5:16
Both
both describe something that produces a real effect or counts for somethingJas 5:16
Only avail
the word "avail" is somewhat old-fashioned and many readers find it vague, blurring the concrete idea of a thing being strong or effective
“be well”
Comparison data is not available for this English gloss yet.
“be in force”
Comparison data is not available for this English gloss yet.
How ischuō differs from similar Greek words
δύναμαιthe general word for being able or capable; this word adds the note of real strength equal to the task, and can tip over into prevailing or being strong enough
Pictures a contest of force, winning out, prevailing, or overcoming an opponent.Act 19:16Rev 12:8
Measures whether someone has the strength equal to a hard, specific task, often in the negative when they fall short.Mat 26:40Act 15:10
Describes something as being in force or having real, effective weight.Heb 9:17Jas 5:16
Both
Both are used for being able to carry out a particular action, sometimes for the very same event: the disciples' failure to drive out an unclean spirit is told with one word and then the other.Mrk 9:28Mrk 9:18
Covers ability in the broadest sense, including what is possible, permitted, or within someone's power, with no thought of physical strength.Mat 6:24Mat 19:25
States that something is possible in itself or possible for God, where no muscle or effort is in view at all.Mat 3:9Mat 26:53
κατισχύωa strengthened form pointed specifically at overpowering or prevailing against opposition, sharpening the "win out" side of this word
Names an inner capacity: to have the strength or ability to carry out a task, whether or not any opponent is in view. It is the ordinary word for being able to do something.Php 4:13Mrk 5:4Luk 14:30
Can mean to be in good health, physically strong rather than sick. This bodily sense belongs to it alone.Mat 9:12Mrk 2:17
Can mean to be effective or of use, to count for something, so that a thing is fit for its purpose.Mat 5:13Gal 5:6
Both
Both come from the same strength word family and can describe strength succeeding against a resisting force, so that one side fails to overcome a fixed structure.Luk 6:48Mat 16:18
The stronger compound, pointed specifically at winning out over resistance: to overpower an opponent, or to prevail against a force set to hold you off. The strength here is measured against something pushing back.Mat 16:18Luk 23:23
Far more often than not it marks the exact spot where strength gives out: the disciples could not stay awake one hour (Matthew 26:40,Mark 14:37), nobody could tie the man up (Mark 5:4), the disciples could not drive the spirit out (Mark 9:18), the fishermen could not haul the net in (John 21:6), and Stephen's opponents could not hold their ground against him (Acts 6:10).Mat 26:40Mrk 14:37Mrk 5:4Mrk 9:18Jhn 21:6Act 6:10
It can mean simply being well in body rather than being up to a task, as when Jesus says the people who are healthy are not the ones who need a doctor.Mat 9:12Mrk 2:17
It works for things as easily as for people, saying that something carries weight or counts for nothing: salt that has lost its taste is good for nothing (Matthew 5:13), being circumcised or not counts for nothing (Galatians 5:6), a will only takes effect once the person has died (Hebrews 9:17), and a good person's prayer accomplishes a great deal (James 5:16).Mat 5:13Gal 5:6Heb 9:17Jas 5:16
It can mean winning a contest outright, coming off stronger than the other side: one man overpowered a whole group (Acts 19:16), the message about the Lord kept gaining ground (Acts 19:20), and the dragon and his angels lost the fight in heaven (Revelation 12:8).Act 19:16Act 19:20Rev 12:8
It is at home in ordinary, unspiritual settings all over the New Testament, from a builder who cannot finish his tower and gets laughed at (Luke 14:29,Luke 14:30) to a manager too weak to dig ditches (Luke 16:3) and sailors who barely manage to secure the ship's boat (Acts 27:16).Luk 14:29Luk 14:30Luk 16:3Act 27:16
Both
Both are about real strength measured against a real demand, not about permission or bare possibility, and they meet inside one clause at Philippians 4:13: one word names the power being supplied to Paul, the other names what he is therefore able to face.Php 4:13
Because they sit side by side in that famous line, one word answers the question the other raises: Paul says he is strong enough for anything, and in the same breath says where the strength comes from.Php 4:13
English hides the pairing. Familiar versions read "I can do all things through him who strengthens me", rendered "be able" for the one and "strengthen" for the other, so a reader working from a translation would not guess that two different strength words are doing two different jobs in a single sentence.Php 4:13
The strength always arrives from someone else, and the giver is usually named out loud: Paul thanks Christ for making him strong enough for the work he was handed (1 Timothy 1:12), and says the Lord stood beside him and supplied the strength when every human supporter had walked away (2 Timothy 4:17).1Ti 1:122Ti 4:17
It is the word used to tell readers to be strengthened, so it names something a person is asked to receive rather than something they either have or lack: be strong in the Lord (Ephesians 6:10), be strengthened by the kindness that comes through Christ (2 Timothy 2:1).Eph 6:102Ti 2:1
It can describe a person being built up over a stretch of time, not just meeting one demand: Saul kept getting more and more effective in Damascus (Acts 9:22), and Abraham was made strong while he went on trusting God's promise (Romans 4:20).Act 9:22Rom 4:20
Every place it turns up belongs to Paul's world, whether his own letters (Romans 4:20,Ephesians 6:10,2 Timothy 2:1) or Luke's account of him (Acts 9:22), so it reads as his particular way of talking about where a Christian's ability comes from.Rom 4:20Eph 6:102Ti 2:1Act 9:22
ischuō in the other biblical languages
יָכֹלHebrew“be able”the common Hebrew verb for being able or prevailing, covering both the "be able to" and the "win out" sides of this Greek word
Leans on actual physical strength and bodily health, the raw vigor to do something. When Jesus says the strong have no need of a doctor, the word describes people who are well and able-bodied.Mat 9:12Mrk 2:17
Can describe a thing being effective or legally valid, not just a person being capable: a will only takes force after the maker has died, and faith at work through love is what actually counts.Heb 9:17Gal 5:6
Both
Both name being able to carry out a task. The land could not support Abram and Lot together, and the builder in Jesus' parable was not able to finish what he started.Gen 13:6Luk 14:30
Both mean to prevail or win out over an opponent. Jacob is renamed because he struggled with God and with men and came out on top, and the possessed man in Acts overpowered the sons of Sceva.Gen 32:28Act 19:16
Is the everyday Hebrew word for "can", covering not only strength but what a person is permitted or free to do. Balaam says he cannot go past what the LORD tells him, and the Egyptians may not eat with Hebrews, where the barrier is duty or custom rather than lack of power.Num 22:18Gen 43:32
חָזַקHebrew“to strengthen: strengthen”the Hebrew verb for being or growing strong and so prevailing, closest to this word's sense of strength that is up to the task
Names a person's or thing's capacity to do something, the inner ability to manage or accomplish a task. The disciples "could not" cast out a spirit, and Paul "can do all things" through Christ who strengthens him.Mrk 9:18Php 4:13
Carries a legal sense of being valid or in force. A will or covenant "is of force" only after the death that establishes it, and circumcision "avails" nothing in Christ.Heb 9:17Gal 5:6
Can mean to be good for a purpose, to count for anything. Salt that has lost its savor "is good for nothing" but to be cast out.Mat 5:13
Both
Both name having the strength to prevail, to win out over an opponent or obstacle. The possessed man "prevailed against" the exorcists, just as Israel "prevailed" to put the Canaanites to forced labor.Act 19:16Jdg 1:28
Both can describe a person being or growing strong rather than weak or sick. The strong "that are whole" need no physician, as David "strengthened himself" in the Lord when distressed.Mat 9:121Sa 30:6
Adds the physical act of seizing, grasping, or taking firm hold of something or someone. The angels "laid hold upon" Lot's hand, and a man who "takes hold" of a betrothed woman in the field commits a violent crime.Gen 19:16Deu 22:25
Used of a heart being made hard and unyielding, so that someone refuses to bend or obey. Pharaoh's heart "was hardened" so he would not let Israel go.Exo 7:13Exo 14:4
Means to repair, fortify, or make a structure firm again. The priests "repaired" the breaches of the temple, and the builders each "repaired" a stretch of Jerusalem's wall.2Ki 12:5Neh 3:4
Causative, to strengthen or encourage another person to act with courage. Moses tells Joshua and Israel to "be strong," and the prophet says to "strengthen" the weak hands.Deu 31:6Isa 35:3
Names the ability to carry out one particular act, and the New Testament usually reports that ability running out: the disciples cannot stay awake an hour, the builder cannot finish what he started, the fishermen cannot haul the net in.Mat 26:40Luk 14:30Jhn 21:6
Covers usefulness and legal force, so a thing that no longer works or no longer counts is said to have no strength: salt that is good for nothing, circumcision that counts for nothing, a will that only takes effect once the one who made it has died.Mat 5:13Gal 5:6Heb 9:17
Reaches into bodily health, where the strong are simply the well people, the ones with no need of a doctor.Mat 9:12
Both
Both are the word for getting the upper hand in a contest of power, where one side proves stronger and the other gives way.Jdg 3:10Jdg 6:2Act 19:16Rev 12:8
Both weigh up what a person can rely on in himself, one man making his own wealth and wrongdoing his strength, another admitting he has not the strength for hard digging.Psa 52:7Luk 16:3
Both are the ordinary, everyday verb for being strong in their own language, at home in plain narrative as much as in poetry, which is why Greek writers reach for the one where Hebrew writers reach for the other: a power that takes hold and grows is said to be strong in either tongue.Dan 11:12Act 19:20
Treats strength as a settled quality that someone or something has, above all the strength of God's own hand and of the deep springs he fixed in place.Psa 89:13Pro 8:28
Is used for putting strength into something, whether God is asked to reinforce what he has already done for his people or wisdom is said to give a wise man more backbone than ten rulers give a city.Psa 68:28Ecc 7:19
Carries a Hebrew way of speaking about a hard face, where strength shows up as shameless nerve rather than as muscle: the woman who fronts up without a blush, the wicked man who stares you down.Pro 7:13Pro 21:29
Centers on capability: having the power to carry out a particular action, so again and again it means simply to be able to do a thing.Luk 14:29Mrk 5:4
Reaches into whether something counts, avails, or stands in force: circumcision that avails nothing, a will that has binding legal force.Gal 5:6Heb 9:17
Both
Both can describe being strong enough to overpower or prevail against an opponent.Psa 105:24Act 19:16
Names strength that comes from sheer numbers: a people grows mighty by multiplying until it outweighs those around it.Exo 1:7Gen 26:16
Describes being so vast as to pass beyond counting, the might lying in overwhelming quantity itself.Psa 40:5Psa 139:17
What scholars say about ischuō
The lexica are agreed on the semantic range: BDAG lists (1) to have power or competence, be able, be strong enough (usually with an infinitive), (2) of physical condition, be healthy or well (Matt 9:12;Mark 2:17), (3) of things, to be valid, be in force, or avail (Heb 9:17;Gal 5:6;James 5:16), and (4) to be victorious, prevail, or win out over opposition (Acts 19:16;Rev 12:8). The verb is denominative from the noun ischys (strength, might), and Grundmann in TDNT stresses that it connotes strength adequate to a demand, distinguishing it from the more neutral dynamai. LSJ documents the same classical range from Herodotus and the tragedians onward. Louw-Nida distributes the New Testament occurrences across the domains of capability, health, and force. No significant lexical dispute attaches to the word; the interpretive questions are contextual (e.g. whether Acts 19:20 is intransitive "grew mighty" or "prevailed").
Sources
BDAG, s.v. ἰσχύωlexicon
LSJ, s.v. ἰσχύωlexicon
W. Grundmann, "ἰσχύω, ἰσχυρός, ἰσχύς", TDNT 3:397-402dictionary
EDNT, s.v. ἰσχύωdictionary
Louw-Nida, Greek-English Lexicon of the New Testament Based on Semantic Domains, s.v. ἰσχύωlexicon