Word Study for G2545 (καίω) | Strong's Concordance

kaíō /kah'-yo/ Ask about this word

Rootapparently a primary verb

Meaningto set on fire, i.e. kindle or (by implication) consume

KJV usageburn, light.

Word Study

In depth

A plain-language study of kaíō — the range of meaning it carries, how Scripture actually uses it, and where it points. Written for readers who don’t know the original language.

Core Meaning & Semantic Range

The Greek word kaíō, represented by G2545, is a primary verb that means to set on fire, i.e. kindle or (by implication) consume. It appears 12 times across 12 unique verses in the Bible. Its application covers both the literal act of igniting a flame and the figurative or divine act of consumption by fire.

Biblical Occurrences & Contextual Analysis

In biblical usage, G2545 appears in several key contexts. It is frequently used to describe divine judgment and destruction, as seen in the lake which burneth with fire and brimstone Revelation 21:8 and in the fate of fruitless branches that are cast into the fire and burned John 15:6. The word is also used to signify illumination, such as when men light a candle Matthew 5:15 or when John the Baptist is described as a burning and shining light John 5:35. It can also convey intense spiritual or emotional experience, as when the disciples' hearts burn within them upon understanding the scriptures Luke 24:32.

Related Words & Concepts

Several related words expand upon the concepts of fire, light, and consumption:

G4442 pŷr (fire): This is the literal element of combustion, often paired with G2545 to describe the means of burning, such as the "great mountain burning with fire" Revelation 8:8 or the mount that burned with fire at Sinai Hebrews 12:18.
G3088 lýchnos (a portable lamp or other illuminator): This is the object being lit. It is used in the command to keep your lights burning Luke 12:35 and in the description of a candle that men light to illuminate a house Matthew 5:15.
G3583 xēraínō (to desiccate; by implication, to shrivel, to mature): This word describes a state of readiness for burning. A branch that does not abide in Christ first "is withered" before it is gathered to be burned John 15:6.
G906 bállō (to throw): This verb often precedes the act of burning, describing how something is delivered to the fire, as when the beast and false prophet were cast alive into the lake of fire Revelation 19:20.

Theological Significance

The theological weight of G2545 is significant, touching on themes of judgment, readiness, and divine revelation.

Divine Judgment: The word is a stark descriptor of final judgment, portraying the ultimate consequence for the unrepentant in the "lake of fire burning with brimstone" Revelation 19:20. It also serves as a warning for unfruitfulness John 15:6.
Faithful Witness: To have one's lights burning Luke 12:35 is a command for spiritual vigilance and readiness. It is also a mark of a powerful witness, as John the Baptist was a "burning and a shining light" John 5:35.
Spiritual Fervor: The term is used to describe a heart ignited by divine truth. The disciples' hearts burn when they finally understand the scriptures as explained by the risen Christ, signifying an intense spiritual passion Luke 24:32.

Summary

In summary, G2545 is a powerful word that conveys more than the simple act of setting something on fire. It carries the dual biblical concepts of destructive judgment and purifying light. From the warning of a consuming fire to the call for a burning lamp of testimony, kaíō serves as a critical term for understanding divine justice, spiritual readiness, and the passionate response of a heart set ablaze by God's word.

How the KJV Renders It

Translation

Strong’s lists the renderings but not their weight. These are counted from the King James text of the tagged verses — the bar under each is how often the translators actually reached for it. Select one to filter the occurrences below.

Grammatical Forms

Morphology

In the Greek New Testament, this word appears as a verb and an adjective across 14 occurrences, inflected in 12 grammatical forms — each row is one form, and the bar is how often it is that form.

Present Passive Indicative 3rd Singular 2×
Present Passive Participle Nominative Singular Masculine 2×
Aorist Middle Deponent Subjunctive 1st Singular 1×
Genitive Singular Feminine 1×
Perfect Passive Participle Dative Singular Neuter 1×
Present Active Indicative 3rd Plural 1×
Present Passive Participle Dative Singular Feminine 1×
Present Passive Participle Genitive Singular Feminine 1×
Present Passive Participle Nominative Plural Feminine 1×
Present Passive Participle Nominative Plural Masculine 1×
Present Passive Participle Nominative Singular Feminine 1×
Present Passive Participle Nominative Singular Neuter 1×

Nominative: The subject of the verb.
Genitive: Possession or source — often "of".
Dative: The indirect object — often "to" or "for".
Singular: One.
Plural: More than one.
Masculine: Masculine grammatical gender.
Feminine: Feminine grammatical gender.
Neuter: Neuter grammatical gender.
1st: First person — the speaker ("I"/"we").
3rd: Third person — the one spoken about ("he"/"they").
Present: Action in progress or repeated — happening now or continually.
Aorist: Action viewed as a single whole — usually a simple past event.
Perfect: A completed act whose results continue.
Active: The subject performs the action.
Passive: The subject is acted upon.
Middle Deponent: Middle in form but active in meaning.
Indicative: A plain statement of fact.
Subjunctive: Possibility or purpose — "might", "should".
Participle: A verbal adjective — describes while carrying the verb's action.

Theographic Context

Context

The people, places, and span of history the verses containing this word touch on — drawn from the theographic tagging of Scripture. Select any name to isolate its verses in the occurrence list.

Biblical Distribution

Distribution

Appears in 12 verses across 6 of the 27 books. Most frequent in Revelation (5 verses); never once in the other 21.

Matthew

Luke

John

1 Corinthians

Hebrews

Revelation

Every Occurrence

Concordance

Every verse where the word is tagged in the King James text. Filter by book, by the English word the translators chose, or search within the verses.

Sources. Definition and numbering: James Strong, Exhaustive Concordance of the Bible (1890). Morphology: STEPBible / Tyndale House (CC BY). Verse tagging: the King James text keyed to Strong’s numbers. Every count on this page is computed from the tagged corpus, not estimated.