HEART (Heb. לֵב, lev, pl. לִבּוֹת, libbot; לֵבָב, levav, pl. לְבָבוֹת, levavot). The corresponding Hebrew words only sometimes have the meanings in question but many translators and writers on Bible are, or act as if they were, largely unaware of the fact.
STRICTLY ANATOMICAL SENSES OF LEV AND LEVAV
Senses That Do Not Include the Heart
The current English translations reveal an awareness that in Nahum 2:8  levav means not heart but breast and rightly represent the women as "beating their breasts"; but breast is no less certainly the meaning of lev in Exodus 28:29–30 (three times in all). Again, in II Samuel 18:14–15, since it is only the attack of 10 of Joab's henchmen that finishes Absalom off after their leader has stuck three darts into the victim's lev, those darts must have been stuck, not into his heart, but into his breast. Somewhat similar is the case of II Kings 9:23–24. Jehoram is trying to flee from Jehu in his chariot, but an arrow from Jehu's bow overtakes him and strikes him "between the arms." Now, the rendering of some recent Bible translations (most recently NEB), "between the shoulders," is perhaps too free, but it is historically correct, since it can be seen on contemporary Assyrian reliefs that the lowness of the chariot floor compelled the charioteer to extend his arms horizontally when, like Jehoram here (verse 23), he held the reins in his hands. Add to this that the ground was level (Jezreel), and Jehu only a short distance behind Jehoram, and one must wonder what view of the course of the arrow through the hapless Omrid's chest was adopted by the same translators to account for the statement that "the arrow pierced his heart." What the words va-yeẓe (wa-yeẓeʾ) ha-ḥeẓi mi-libbo
This is what lev means in Isaiah 33:18; Psalms 19:15; 49:4; Job 8:10; Ecclesiastes 5:1. Lev is either parallel to peh ("mouth") or associated with the root hgy (which always denotes audible sounds, including the coo of the dove (Isa. 38:14; 59:11), the growl of the lion (Isa. 31:4), and the twang of the lyre (Ps. 92:4), and never silent meditation), or both, with the exception of Job 8:10, in which lev alternates with the peh of the otherwise identical phrase in 15:13. In fact, lev is the proper word for "throat" in biblical Hebrew, garon taking its place only where the former would be misunderstood (as where loʾ yehgu be-libbam would have meant not, "They cannot utter sounds with their throats," but "They do not speak sincerely," see Hos. 7:14).
Senses that Include the Heart
Even where the word lev clearly refers to something inside the body cavity, it does not always mean specifically the heart. It doubtless does when it is paired with "kidneys" (Jer. 11:20; 17:10; Ps. 7:10; 73:21), but probably more often it merely conveys the general idea of "the insides, the interior of the body"; and from this sense derives its use with yam(mim) ("sea(s)") and ha-shamayim ("the air" or "space") to express the notions "(far) out at sea" and "(high) up in the air (in space)" (Ex. 15:8; Ezek. 27:4, 25–27; 28:2, 8; Ps. 46:3; Prov. 23:34).
NOT STRICTLY ANATOMICAL SENSES OF LEV AND LEVAV
The interior of the body is conceived of as the seat of the inner life, of feeling and thought. Strong feeling is conceived of as a stirring or heating of the intestines (meʿayim) – Isaiah 16:11; Jeremiah 4:19 ; Lamentations 1:20 – as well as of the heart – Deuteronomy 19:6; Jeremiah 48:36; Psalms 39:4. Gladness is a function not only of the heart (e.g., Prov. 23:15) but also of the kidneys (Prov. 23:16; cf. Jer. 12:2b), which also urge a certain course on a man. But it is the lev(av) that figures most often in references to the inner life, both emotional and – and this is its special sphere – intellectual. That is why when lev(av) is mentioned alone it is often hard to decide whether the underlying physical concept is specifically the heart or the inwards generally. At any rate, the Bible never mentions about the lev(av) anything that is literally physical, such as a heartbeat; nor does it ever mention any literal pain or ailment of it. That somebody's "heart" is sick means that he is grieving; that Israel's "heart" is obstructed (older translations, regrettably, "uncircumcised") signifies that it is religiously stubborn and intractable – cutting away the obstruction of Israel's "heart" of course means making it religiously reasonable. So, too, that a man says something "in his heart" means that he says it to himself, or thinks it; that he is "wise of heart" means that he is intelligent or skillful. One who has no "heart" is a dolt. A faithful English translation is precisely one that in most cases does not contain the word "heart," but either substitutes "mind," or sometimes "spirit," or – quite often – does not render the noun at all; for it is often hard to feel, let alone express, the differences between such pairs as "gladness of 'heart'" and plain "gladness," "he rejoiced 'in his heart'" and the bare "he rejoiced," etc. On the other hand, in the interests of both aesthetics and usefulness, "heart" should be substituted in English for the emotional kidneys and intestines of biblical Hebrew: the King James "my bowels were moved for him" (Song 5:4) is not either more beautiful or more enlightening than something like "my heart yearned for him." Finally, on the one hand the word levav illustrates biblical Hebrew's lack of a terminology for distinguishing clearly between mind (or "soul") and body; for when Psalms 104:15 says that bread fortifies a man's levav while wine cheers a man's levav, the first levav means "insides" if not actually "body," but the second one means "spirit." Nevertheless, the words lev and levav enable the language to come close to distinguishing between the two, the former by juxtaposition with basar (בָּשָׂר) the latter by juxtaposition with she'er (שְׁאֵר), two words meaning "body" (lit. "flesh"; see Ps. 73:26; 84:3; Eccles 2:3; 11:10). Psalms 73:26 helps us to detect the fact that the word רֹאשׁ (roʾsh; "head") in Isaiah 1:5 is a corruption, due to contamination by the roʾsh in the following verse, of an original sheʾer, the restoration of which yields for Isaiah 1:5b the sense, "Every body (not just the head but the entire body, see verse 6) is sore and every spirit is anguished."
Y.S. Licht, in: EM, 4 (1962), 411–5 (incl. bibl.); H.L. Ginsberg, in: VT, supplement, 16 (1967), 80.