Lexicon

G1080 - gennao

Strong's: G1080 · BLB lookup Pronunciation: ghen-nah'-o Part of speech: verb Root: from a variation of genos, "race, kind, offspring" NT occurrences: frequent, roughly a hundred, concentrated in Matthew's genealogy (Matt 1:2-16), the new-birth discourse (John 3:3-8), and the born of God formula in 1 John

Gennaō is the verb behind two doctrines that sound unrelated and are governed by the same word: the eternal generation of the Son ("begotten, not made") and the new birth of the believer ("born of God"). It is also the word the fourth-century Arian controversy turned on, because "begotten" was read by Arius as conceding that the Son had a beginning.

Semantic range (Thayer / BDAG)

To beget, to father, of the male parent, active voice (Matthew's genealogy)
To bear, to give birth, occasionally of the mother (Luke 1:57)
To be born, passive voice, of natural birth (Matt 2:1; John 9:2)
To be begotten of God, of spiritual regeneration (John 3:3; 1 John 5:1)
Figuratively, to produce or cause, of quarrels produced by foolish speculation (2 Tim 2:23)

Voice does most of the work. The active is "to beget", almost always of a father; the passive is "to be born". Both senses run through the theological uses.

See this page's graph and discover linked topics

NT uses that carry doctrinal weight

The Psalm 2:7 citation, egō sēmeron gegennēka se

You are My Son, Today I have begotten You. (Psalm 2:7, NASB95)

The line is quoted three times in the NT, each time of Christ: Acts 13:33, Hebrews 1:5, and Hebrews 5:5. The verb is perfect active, gegennēka, "I have begotten."

An honest reading has to note that the referent of the "today" is disputed. In Acts 13:33 Paul applies the line in a resurrection-and-enthronement context, and many commentators read all three citations declaratively: the Son is publicly declared to be what He eternally is (compare Rom 1:4, "declared the Son of God with power by the resurrection"). On that reading, Psalm 2:7 is not the primary proof text for eternal generation, and the doctrine rests instead on John 1.14 and John 1.18 (monogenēs), John 5:26 (the Father "granted the Son also to have life in Himself"), and the Father-Son relation as such.

The new birth, John 3:3-8

That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. (John 3:6, NASB95)

Gennaō in the passive with anōthen ("from above" / "again") is the vocabulary of regeneration. The same verb that names the Son's eternal relation to the Father names the believer's derived, created sonship. The two are not the same relation, and the NT keeps them apart lexically at one crucial point: believers are tekna, children, while Jesus is huios, Son (John 1:12 against 1:14), and only Jesus is monogenēs.

Born of God, 1 John

The perfect passive participle gegennēmenos ek tou theou is the structural refrain of 1 John (2:29; 3:9; 4:7; 5:1; 5:4; 5:18). The perfect tense matters: a completed begetting with an abiding result, not a repeated event.

The Nicene use, gennēthenta ou poiēthenta

The Nicene Creed confesses the Son as gennēthenta ou poiēthenta, begotten, not made, and the whole fourth-century controversy is compressed into those four words.

The Arian argument. Begetting implies a beginning. Every son is younger than his father. Therefore, if the Son is begotten, "there was when He was not" (ēn pote hote ouk ēn), and He is a creature, however exalted.

The Nicene reply, in three moves.

Begetting and making are different categories. A creature is made by will, out of nothing, and is of a different nature than its maker. A son is begotten according to nature and is of the same nature as his father. Athanasius presses exactly this: creating belongs to God's will, begetting to God's nature (Orationes contra Arianos I.29; II.2). To make the Son a creature is to say God's nature is barren.
The generation is eternal, not temporal. Origen had already argued that the Father always begets the Son (aei gennatai), so the relation has no before and after (De Principiis I.2.4). Human begetting is temporal because human fathers are temporal; the argument from human analogy proves nothing about a timeless begetter.
The generation is necessary, not voluntary. The Father does not choose to have a Son the way He chooses to create a world. The Son is not contingent, so there is no possible state of affairs in which the Father is Sonless.

The Arian objection therefore trades on importing the temporal and volitional features of creaturely begetting into a relation the creed defines by contrast with making. See Arianism and Trinity Invented at Nicaea Objection Defeater.

Lexical caution

Monogenēs (G3439 - monogenes, "only begotten" in older translations) is not built from gennaō. It is monos ("only") plus genos ("kind"), so the emphasis falls on one of a kind, unique, not on an act of begetting. Arguments for eternal generation that lean on the etymology of monogenēs are leaning on the wrong root. The doctrine is better argued from the Father-Son relation itself, from John 5:26, and from the ek tou Patros language of John 1:14, than from a false etymology.

Theological force

Same nature, not lesser nature. What a father begets is of his own kind. Begotten-language, correctly read, is an argument for the Son's deity, not against it.
No divine solitude. If the Father eternally begets, the Father was never without the Son, so love and relation are internal to God rather than acquired at creation. See Trinity Love-Overflow Argument.
Adoption is derivative. Believers are begotten of God by the Spirit, in a created and gracious sense. The Son's sonship is the pattern, never the peer, of ours.

Notes

Lexical workspace for gennaō.