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Vine's Expository Dictionary of NT Words [1]

1: Κλαίω (Strong'S #2799 — Verb — klaio — klah'-yo )

"to wail," whether with tears or any external expression of grief, is regularly translated "weep" in the RV; once in the AV it is rendered "bewail,"  Revelation 18:9 . See Weep.

 John 11:35

2: Κόπτω (Strong'S #2875 — Verb — kopto — kop'-to )

primarily, "to beat, smite;" then, "to cut off,"  Matthew 21:8;  Mark 11:8 , is used in the Middle Voice, of beating oneself, beating the breast, as a token of grief; hence, "to bewail,"  Matthew 11:17 (RV, "mourn," for AV, "lament");   Matthew 24:30 , "mourn;"  Revelation 1:7 (RV, "mourn;" AV, "wail"); in   Luke 8:52;  23:27 "bewail;" in   Revelation 18:9 , "wail" (for AV, "lament"). See Cut , Mourn. Cp. kopetos, "lamentation,"   Acts 8:2 .

3: Πενθέω (Strong'S #3996 — Verb — pentheo — pen-theh'-o )

denotes "to lament, mourn," especially for the dead; in  2—Corinthians 12:21 , RV, "mourn" (AV, "bewail"). See also  Revelation 18:11,15,19 . Cp. penthos, "mourning." See Mourn.

 Matthew 11:17 Luke 7:32 Luke 23:27 John 16:20 Matthew 2:18 Matthew 2:18 2—Corinthians 7:7

King James Dictionary [2]

BEWA'IL, be and wail. To bemoan to lament to express sorrow for. It expresses deep sorrow as, to bewail the loss of a child.

The true penitent bewails his ingratitude to God.

BEWA'IL, To express grief.

Webster's Dictionary [3]

(1): (v. i.) To express grief; to lament.

(2): (v. t.) To express deep sorrow for, as by wailing; to lament; to wail over.

International Standard Bible Encyclopedia [4]

bē̇ - wāl ´ (κόπτω , kóptō ): In the middle voice, this word has the thought of striking on the breast and of loud lamentation, so common among oriental people in time of great sorrow. It is used to express the most intense grief, a sorrow that compels outward demonstration ( Luke 8:52;  Luke 23:27 ). A striking instance of this grief is that of the daughter of Jephthah ( Judges 11:37;  Leviticus 10:6 ). See Burial , IV, 4, 5, 6; Grief .