The Greek word for "dead" found in the New Testament is the word necros. Here are a few lexical entries for this word:
Friberg:
nekros, a,, o,n dead; (1) of persons; (a) literally; (i) of human beings and animals no longer physically alive dead, lifeless, deceased (AC 28.6; JA 2.26a); (ii) substantivally o` n. dead person (LU 7.15); oi` nekroi, the dead, dead people (MK 12.26); (b) figuratively; (i) of persons unable to respond to God because of moral badness or spiritual alienation dead, powerless (EP 2.1, 5); (ii) of persons regarded as dead because of separation dead (LU 15.24, 32); (iii) of persons no longer under the control of something dead to (RO 6.11); (2) of things; literally lifeless (e.g. idols); figuratively, of what is of no benefit morally or spiritually utterly useless, completely ineffective (HE 6.1; JA 2.26b)
United Bible Society:
nekros , a, , o,n dead, lifeless ( o` nÅ a dead person, corpse; evpi. nÅ in the case of dead persons or at death He 9.17); useless, ineffective
Liddell-Scott:
nekros( a,( o,n, dead, Pind.:-Comp. &o,teroj Anth. II usually as Subst. o`, = ne,kuj, a dead body, corpse, Hom., etc.:-in pl. the dead, as dwellers in the nether world, Od.; tou.j e`autw/n n. their own dead, of those killed in battle, Thuc.
Thayers (a lot of the Hebrew won't copy right):
nekros, nekra,, nekro,n (akin to the Latin neco, nex (from a root signifying `to disappear' etc.; cf. Curtius, sec. 93; Fick i., p. 123; Vanicek, p. 422f)), the Septuagint chiefly for tme; dead, i. e.:
1. properly, a. one that has breathed his last, lifeless: Matt. 28:4; Mark 9:26; Luke 7:15; Acts 5:10; 20:9; 28:6; Heb. 11:35; Rev. 1:17; evpi, nekroi/j, if men are dead (where death has occurred (see evpi,, Buttmann, 2 a. e., p. 233a at the end)), Heb. 9:17; evgei,rein nekrou,j, Matt. 10:8; 11:5; Luke 7:22; hyperbolically and proleptically equivalent to as if already dead, sure to die, destined inevitably to die: to, sw/ma, Rom. 8:10 (to, sw/ma and to, swma,tion fu,sei nekro,n, Epictetus diss. 3, 10, 15 and 3, 22, 41; in which sense Luther called the human body, although alive, einen alten Madensack (cf. Shakespeare's "thou worms-meat!")); said of the body of a dead man (so in Homer often; for hl'ben> a corpse Deut. 28:26; Isa. 26:19; Jer. 7:33; 9:22; 19:7): meta, tw/n nekrw/n, among the dead, i. e. the buried, Luke 24:5; qa,yai tou,j nekrou,j, Matt. 8:22; Luke 9:60; ovste,a nekrw/n, Matt. 23:27; of the corpse of a murdered man, ai-ma w`j nekrou/, Rev. 16:3 (for gWrh', Ezek. 37:9; for ll'x',thrust through, slain, Ezek. 9:7; 11:6). b. deceased, departed, one whose soul is in Hades: Rev. 1:18; 2:8; nekro,j h=n, was like one dead, as good as dead, Luke 15:24,32; plural, 1 Cor. 15:29; Rev. 14:13; evn Cristw/|, dead Christians (see evn, I. 6 b., p. 211b), 1 Thess. 4:16; very often oi` nekroi, and nekroi, (without the article; see Winer's Grammar, p. 123 (117) and cf. Buttmann, 89 (78) note) are used of the assembly of the dead (see avna,stasij, 2 and evgei,rw, 2): 1 Pet. 4:6; Rev. 20:5,12f; ti,j avpo, tw/n nekrw/n, one (returning) from the dead, the world of spirits, Luke 16:30; evk nekrw/n, from the dead, occurs times too many to count (see avna,stasij, avni,sthmi, evgeriw): avna,gein tina evk nekrw/n, Rom. 10:7; Heb. 13:20; zwh, evk nekrw/n, life springing forth from death, i. e. the return of the dead to life (see evk, I. 5), Rom. 11:15; prwto,tokoj evk tw/n nekrw/n who was the first that returned to life from among the dead, Col. 1:18; also prwto,tokoj tw/n nekrw/n Rev. 1:5; zowpoi,ein tou,j nekrou,j Rom. 4:17; evgei,rein tina avpo, tw/n nekrw/n, to rouse one to quit (the assembly of) the dead, Matt. 14:2; 27:64; 28:7; kri,nein zw/ntaj kai, nekrou,j, 2 Tim. 4:1; 1 Pet. 4:5; krith,j zw,ntwn kai, nekrw/n, Acts 10:42; nekrw/n kai, zw,ntwn kurieu,ein, Rom. 14:9. c. destitute of life, without life, inanimate (equivalent to a;yucoj): to, sw/ma cwri,j pneu,matoj nekro,n evstin, James 2:26; ouvk evstin (o`) Qeo,j nekrw/n avlla, zw,ntwn, God is the guardian God not of the dead but of the living, Matt. 22:32; Mark 12:27; Luke 20:38.
2. tropically: a. (spiritually dead, i. e.) "destitute of a life that recognizes and is devoted to God, because given up to trespasses and sins; inactive as respects doing right": John 5:25; Rom. 6:13; Eph. 5:14; Rev. 3:1; with toi/j paraptw,masin (the dative of cause (cf. Winer's Grammar, 412 (384f))) added, Eph. 2:1,5; evn (but T Tr WH omit evn) toi/j paraptoij Col. 2:13; in the pointed saying a;fej tou,j nekrou,j qa,yai tou,j e`autw/n nekrou,j, leave those who are indifferent to the salvation offered them in the gospel, to bury thee bodies of their own dead, Matt. 8:22; Luke 9:60. b. universally, destitute of force or power, inactive, inoperative: th/| a`marti,a, unaffected by the desire to sin (cf. Winer's Grammar, 210 (199); Buttmann, sec. 133, 12), Rom. 6:11; of things: a`marti,a, Rom. 7:8; pi,stij, James 2:17,20 (R G), 26; e;rga, powerless and fruitless (see e;rgon, 3, p. 248b bottom), Heb. 6:1; 9:14. (Cf. qnhto,j, at the end)
In Thayers, pay special attention to the second definition, because that touches on the spiritual aspects of death. Notice a popular usage of the word death in a metaphorical sense refers to something that is "useless." Also, notice that in the normal usage of the word, separation of body and soul is not even mentioned.
