The Heb. word דּוֹר, H1887, is of broader meaning and includes the thought of an era of time, a period and thence a generation. The word has no reference to begetting. The phrase דוֹר־וָדֹ֖ור “an age and an age” means “eternity,” “forever.” The same phrase is used in Ugaritic texts. The word is used (usually in the sing.) of many generations to come, as well as of a specific living generation, such as the one which died in the wilderness (Deut 2:14). The average length of a generation is often assumed to be forty years, for in the wilderness all the men over twenty died within that time. This would give a measure not of the period from a man’s birth to his children’s birth (more like thirty years), but would give the measure of a lifetime sixty years or more. This is apparently the meaning of Genesis 15:13, 16. Four generations equal 400 years if a generation be counted as a long lifespan. There is no statement in the Bible that the forty-year span of the rule of Solomon, of David, and of four of the judges was a round number for one generation. The forty-year figure in the Moabite Stone has also now been shown to be an accurate figure (F. M. Cross and D. N. Freedman, Early Hebrew Orthography, American Oriental Series, vol. 36 , 39, 40).
The word תּוֹלֵדוֹת, H9352, comes from the root meaning “to bear a child” and is used in many OT genealogies. It may well refer also to family history in general (Gen 2:4; 6:9; 25:19; 37:2).
In the NT, the word γενέα is usually tr. “generation” (in the KJV, thirty-six times), but is also tr. “age,” “nation,” and “time.” It is used in the genealogy of Matthew 1. Many times Jesus speaks of the faithless and perverse generation (Matt 17:17, etc.) where the reference could equally be to the Jewish nation (cf. Phil 2:15). In the RSV, such passages are tr. by “generation.”
A problem v. is Matthew 24:34 and parallels. Some argue for the strict meaning and claim that Christ mistakenly expected the end in His own time. Others note that standard lexicons and other studies allow the meaning “race” or “clan” or “nation,” and hold that the v. predicts the continuation of the Jewish people until Christ’s return. Zahn’s Commentary (in loc.) argues that “this generation” of Matthew 24:34 refers to the “this generation” of 23:36, and is in contrast to “that day and hour” of Matthew 24:36. The former expression refers to troubles applicable to the disciples’ own day; the latter refers to eschatological events.
G. F. Moore, Judges (on the number forty), ICC, xxxviii (1903); H. L. Ellison, “Kings” (on the number forty), NBC 307; C. H. Dodd, The Authority of the Bible (Torchbook, 1958), 233; H. A. Kent, Jr., “Matthew,” WBC, 973 (on Matt 24:34).
International Standard Bible Encyclopedia (1915)
(Latin generatio, from genero, "beget"):
(1) The translation
(a) of dor, "circle," "generation," hence, "age," "period," "cycle": "many generations" (De 32:7);
(b) the people of any particular period or those born about the same time: "Righteous before me in this generation" (Ge 7:1); "four generations" (Job 42:16);
(c) the people of a particular class or sort, with some implied reference to hereditary quality; the wicked (De 32:5; Pr 30:11); the righteous (Ps 14:5; 112:2).
(2) toledhoth, "births," hence
(a) an account of a man and his descendants: "The book of the generations of Adam" (Ge 5:1);
(b) successive families: "The families of the sons of Noah, after their generations" (Ge 10:32);
(c) genealogical divisions: "The children of Reuben .... their generations, by their families" (Nu 1:20); (d) figurative, of the origin and early history of created things: "The generations of the heavens and of the earth" (Ge 2:4).
(3) genea, "a begetting," "birth," "nativity," therefore
(a) the successive members of a genealogy: "All the generations from Abraham unto David" (Mt 1:17);
(b) a race, or class, distinguished by common characteristics, always (in the New Testament) bad: "Faithless and perverse generation" (Mt 17:17);
(c) the people of a period: "This generation shall not pass away" (Lu 21:32);
(d) an age (the average lifetime, 33 years): "Hid for (Greek "from the") ages and (from the) generations" (Col 1:26). The term is also by a figurative transference of thought applied to duration in eternity: "Unto all generations for ever and ever" (Eph 3:21) (Greek "all the generations of the age of the ages").
(4) genesis, "source," "origin": "The book of the generation of Jesus Christ" (Mt 1:1; the American Revised Version, margin "The genealogy of Jesus Christ").
(5) gennema, "offspring," "progeny"; figurative: "O generation of vipers" (Lu 3:7 the King James Version).
(6) genos, "stock," "race," in this case spiritual: "But ye are a chosen generation" (1Pe 2:9; the American Standard Revised Version "an elect race").