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Morrish Bible Dictionary [1]

Three Hebrew words are translated 'eternal.'

1. ad: very often translated 'for ever,' and with another word, olam , 'for ever and ever.' "The Lord shall reign for ever and ever."  Exodus 15:18 . "The Lord is king for ever and ever."  Psalm 10:16 : cf. also  Psalm 45:6;  Psalm 48:14;  Psalm 52:8 .  Micah 4:5 . Ad is also translated 'everlasting:' "the everlasting Father," or "Father of the everlasting age."   Isaiah 9:6 . Also 'eternity;' "the high and lofty One that inhabiteth eternity."  Isaiah 57:15 .

2. olam , signifying 'everlasting,' 'never ending.' It is often translated 'for ever:' "his mercy endureth for ever,"  1 Chronicles 16:41; and 'everlasting:' "the everlasting God."  Genesis 21:33;  Psalm 90:2;  Psalm 93:2;  Psalm 103:17 . "I will make thee an eternal excellency."  Isaiah 60:15 .

3. qedem, 'ancient, that which is before.' "The eternal God is thy refuge."  Deuteronomy 33:27 . "Art thou not from everlasting?"  Habakkuk 1:12 . "God is my King of old."  Psalm 74:12 .

4. In the N.T., ἀΐδιος, 'perpetual:' occurs only in   Romans 1:20 , "his eternal power and Godhead;" and  Jude 6 , "reserved in everlasting chains."

5. αἰών, 'age, duration, ever.' With a preposition 'unto the ages' is often translated 'for ever;' and, when repeated, 'for ever and ever.' "He that eateth of this bread shall live for ever."  John 6:58 . "Christ abideth for ever."  John 12:34 . "To whom be glory for ever and ever."  Galatians 1:5 . "According to the eternal purpose."  Ephesians 3:11 . "Now unto the king eternal . . . . be honour and glory for ever and ever."  1 Timothy 1:17 . This word is often translated 'world,' but may at times be better rendered 'age,' as "be not conformed to this age,"  Romans 12:2; and 'for ever and ever' may be translated 'to the ages of ages,' though the meaning would be the same.

6. αἰώνιος,from αἰών, signifying 'ever enduring.' It is always translated 'eternal' or 'everlasting,' except in  Romans 16:25 , "since the world began," or "in the times of the ages."  2 Timothy 1:9;  Titus 1:2 , "before the world began," or, "before the ages of time;" and  Philippians 15 , "for ever." This word is applied to God Himself as "the everlasting God."  Romans 16:26; to the Holy Spirit.  Hebrews 9:14; to redemption.  Hebrews 9:12; inheritance.  Hebrews 9:15; salvation.  Hebrews 5:9; glory.  1 Peter 5:10; and constantly to life.  John 3:15,16,36 . On the other hand it is applied to punishment,  Matthew 25:46; damnation,  Mark 3:29; destruction,  2 Thessalonians 1:9; and fire,  Jude 7 : cf.  Isaiah 33:14 .

The above passages show that the same word is used for the existence of God Himself; for the salvation and blessedness of the saved; and for the punishment of the wicked.

Vine's Expository Dictionary of NT Words [2]

1: Αἰών (Strong'S #165 — Noun Masculine — aion — ahee-ohn' )

"an age," is translated "eternal" in  Ephesians 3:11 , lit., "(purpose) of the ages" (marg.). See Age.

2: Αἰώνιος (Strong'S #166 — Adjective — aionios — ahee-o'-nee-os )

"describes duration, either undefined but not endless, as in  Romans 16:25;  2—Timothy 1:9;  Titus 1:2; or undefined because endless as in  Romans 16:26 , and the other sixty-six places in the NT.

 2—Corinthians 4:18 Philemon 1:15 Romans 16:26 1—Timothy 6:16 1—Peter 5:10 Hebrews 9:14 Hebrews 9:12 Hebrews 5:9 2—Peter 1:11 Luke 1:33 John 3:16 John 10:28 2—Corinthians 5:1 1—Corinthians 15:53 Matthew 25:46 Titus 1:2 Mark 3:29 Hebrews 6:2 Matthew 18:8 25:41 Jude 1:7 Mark 9:43 2—Thessalonians 1:9

3: Ἀΐδιος (Strong'S #126 — Adjective — aidios — ah-id'-ee-os )

see Everlasting.

Hawker's Poor Man's Concordance And Dictionary [3]

Eternal, Eternity

The Scripture sense of these terms, in reference to the persons of the Godhead and the events connected with them, are in the strictest sense of the word, for ever and ever. Very solemn, and yet very blessed, and full of the highest consolation, are those views of the eternity of Jehovah and his purposes in salvation. How infinitely sublime are those Scriptures! "Thus saith the high and lofty One that inhabiteth eternity, whose name is Holy." ( Isaiah 57:15) "For I lift up my hand to heaven, and say, I live for ever." ( Deuteronomy 32:40) "The eternal God is thy refuge, and underneath are the everlasting arms." ( Deuteronomy 33:27) And JEHOVAH, in a threefold character of persons, Father, Son, and Holy Ghost, is thus described in the eternity of his nature and essence, so Christ the Mediator, by virtue of the union of the manhood with the GODHEAD, is declared by JEHOVAH to be eternal. "Thy throne, O God, is for ever and ever." ( Psalms 45:6;  Hebrews 1:8) "The Lord sware, and will not repent; Thou art a Priest for ever, after the order of Melchizedec." ( Psalms 110:4) And hence, in Christ and by Christ, and from an union with him, all that is connected in the blessed work of salvation is of eternal duration. The covenant is declared to be an everlasting covenant, ordered in all things and sure. ( 2 Samuel 23:5;  Jeremiah 32:40) The gospel is called an everlasting gospel. ( Revelation 14:6) Redemption is said to be an eternal redemption. ( Hebrews 9:12) And the consequence certainly follows from these properties, that the glory purchased by an eternal redemption is an eternal weight of glory. So the apostle to the Corinthians calls it,  2 Corinthians 4:17. (See  Hebrews 5:9;  1 Peter 5:10;  1 John 5:11)

King James Dictionary [4]

ETER'NAL, a. L. oeternus, composed of oevum and ternus, oeviternus, Varro. The origin of the last component part of the word is not obvious. It occurs in diuturnus, and seems to denote continuance.

1. Without beginning or end of existence.

The eternal God is thy refuge.  Deuteronomy 33

2. Without beginning of existence.

To know whether there is any real being, whose duration has been eternal.

3. Without end of existence or duration everlasting endless immortal.

That they may obtain the salvation which is in Christ Jesus with eternal glory.  2 Timothy 2

What shall I do, that I may have eternal life?  Matthew 19

Suffering the vengeance of eternal fire.  Jude 1:7 .

4. Perpetual ceaseless continued without intermission.

And fires eternal in thy temple shine.

5. Unchangeable existing at all times without change as eternal truth.

ETER'NAL, n. An appellation of God.

Webster's Dictionary [5]

(1): ( a.) Without end of existence or duration; everlasting; endless; immortal.

(2): ( a.) Continued without intermission; perpetual; ceaseless; constant.

(3): ( a.) Existing at all times without change; immutable.

(4): ( a.) Without beginning or end of existence; always existing.

(5): ( a.) Exceedingly great or bad; - used as a strong intensive.

(6): ( n.) One of the appellations of God.

(7): ( n.) That which is endless and immortal.

International Standard Bible Encyclopedia [6]

ē̇ - tûr´nal ( עולם , ‛ōlām  ; αἰώνιος , aiō̇nios , from αἰών , aiō̇n ): The word "eternal" is of very varying import, both in the Scriptures and out of them.

1. ‛Ōlām

In the Old Testament, the Hebrew word ‛ōlām is used for "eternity," sometimes in the sense of unlimited duration, sometimes in the sense of a cycle or an age, and sometimes, in later Hebrew, in the signification of world. The Hebrew ‛ōlām has, for its proper New Testament equivalent, aiōn , as signifying either time of particular duration, or the unending duration of time in general. Only, the Hebrew term primarily signified unlimited time, and only in a secondary sense represented a definite or specific period. Both the Hebrew and the Greek terms signify the world itself, as it moves in time.

2. Aiōn , Aiōnios

In the New Testament, aiōn and aiōnios are often used with the meaning "eternal," in the predominant sense of futurity. The word aiōn primarily signifies time, in the sense of age or generation; it also comes to denote all that exists under time-conditions; and, finally, superimposed upon the temporal is an ethical use, relative to the world's course. Thus aiōn may be said to mean the subtle informing spirit of the world or cosmos - the totality of things. By Plato, in his Timaeus , aiōn was used of the eternal Being, whose counterpart, in the sense-world, is Time. To Aristotle, in speaking of the world, aiōn is the ultimate principle which, in itself, sums up all existence. In the New Testament, aiōn is found combined with prepositions in nearly three score and ten instances, where the idea of unlimited duration appears to be meant. This is the usual method of expressing eternity in the Septuagint also. The aiōnios of  2 Corinthians 4:18 must be eternal, in a temporal use or reference, else the antithesis would be gone.

3. Aı́dios

In  Romans 1:20 the word aı́dios is used of Divine action and rendered in the King James Version "eternal" (the Revised Version (British and American) "everlasting"), the only other place in the New Testament where the word occurs being  Judges 1:6 , where the rendering is "everlasting," which accords with classical usage. But the presence of the idea of eternal in these passages does not impair the fact that aiōn and aiōnios are, in their natural and obvious connotation, the usual New Testament words for expressing the idea of eternal, and this holds strikingly true of the Septuagint usage also. For, from the idea of aeonian life, there is no reason to suppose the notion of duration excluded. The word aiōnios is sometimes used in the futurist signification, but often also, in the New Testament, it is concerned rather with the quality, than with the quantity or duration, of life. By the continual attachment of aiōnios to life, in this conception of the spiritual or Divine life in man, the aeonian conception was saved from becoming sterile.

4. Enlargement of Idea

In the use of aiōn and aiōnios there is evidenced a certain enlarging or advancing import till they come so to express the high and complex fact of the Divine life in man. In Greek, aiō̇nes signifies ages, or periods or dispensations. The aiōnes of  Hebrews 1:2 , and  Hebrews 11:3 , is, however, to be taken as used in the concrete sense of "the worlds," and not "the ages," the world so taken meaning the totality of things in their course or flow.

5. Eternal Life

Our Lord decisively set the element of time in abeyance, and took His stand upon the fact and quality of life - life endless by its own nature. Of that eternal life He is Himself the guarantee - "Because I live, ye shall live also" ( John 14:19 ). Therefore said Augustine, "Join thyself to the eternal God, and thou wilt be eternal." See Eternity .