the stomach or belly: the part of the body that takes in and digests food
TranslatabilityDirectCertaintySettled
This is the plainest use of the word. It names the hollow inside of the body where food goes after it is swallowed, and by extension the whole belly. When Jesus says that what enters the mouth passes into the stomach, or when John eats a little scroll that turns his stomach sour, the word points to this ordinary organ.
From the stomach the word stretches naturally to appetite. To speak of people who serve their own belly, or whose god is their belly, is to picture a life ruled by physical craving, with the appetite treated as a master. English keeps the same image when it talks about someone driven by their gut or their stomach, so the sense carries over cleanly.
Nuances
1athe stomach into which food passes, or the hollow inside of a body
Mat 12:40Mat 15:17Mrk 7:19Luk 15:161Co 6:13 (2×)Rev 10:9Rev 10:10
1bthe belly as the seat of bodily appetite, standing for a life ruled by physical craving
Rom 16:18Php 3:19
2
the womb: the part of a mother's body where a child is conceived and carried before birth
TranslatabilityDirectCertaintySettled
The same word that names the stomach also names the womb, the space inside a mother where a child grows. This is by far its most common use in the New Testament, and it fills the birth stories of John the Baptist and Jesus, where a child leaps in the womb or is called the fruit of the womb.
Very often the word appears in the fixed phrase from the mother's womb, which points not to the womb itself so much as to a condition a person has carried since birth. A man born unable to walk is lame from his mother's womb; Paul says God set him apart from his mother's womb. The expression is a natural way of saying from the very start of life.
Nuances
2athe womb in which a child is conceived and grows
2bthe fixed phrase from the mother's womb, pointing to a condition present from birth
Mat 19:12Luk 1:15Act 3:2Act 14:8Gal 1:15
3
the innermost being: the deep inner core of a person, the source of one's inner life
TranslatabilityPartialCertaintyStrong
In one striking use the word does not point to a physical organ at all but to a person's inmost self. This follows an old Hebrew way of speaking, in which the inward parts are pictured as the seat of feeling, longing, and life. When Jesus promises that rivers of living water will flow from within a person, the word marks that deep interior as the spring from which the water comes.
This use is rare and vivid rather than ordinary. English cannot carry it with the plain word belly, which would badly mislead; translators reach instead for the heart, the innermost being, or simply within.
names the stomach, the organ of digestion, with no connection to childbirth at allMat 15:17Mrk 7:191Co 6:13Rev 10:10
stretches metaphorically to a person's inmost being, the source of appetite or of life flowing out, never a literal body partPhp 3:19Jhn 7:38
the plain, ordinary word Luke reaches for throughout his birth narratives, describing an actual pregnancy in the flow of a story rather than in a legal quotationLuk 1:41Luk 1:44
Both
both words can denote the same organ, the womb where a child is carried before birthLuk 1:42Luk 2:23
the technical term the law used for the organ itself, restricted here to the formal rule that every firstborn male who opens the womb belongs to GodLuk 2:23
names the womb specifically as the seat of a woman's capacity to conceive, used to describe a body no longer able to bear a childRom 4:19
γαστήρa near-twin that also spans belly and womb, but in the New Testament is used almost only in the set phrase for being pregnant, having a child in the womb
Names the stomach as the ordinary organ of digestion, where food goes after it is eaten.Mat 15:17Mrk 7:191Co 6:13Luk 15:16
Supplies the formula from his mother's womb, marking a person as set apart, filled with the Spirit, or born with a condition from the very start of life, rather than describing a pregnancy in progress.Luk 1:15Gal 1:15Act 3:2Mat 19:12
Stretches beyond anatomy to name the innermost part of a person, the place something wells up from within, and even the belly of a sea creature that swallows a man whole.Jhn 7:38Mat 12:40
Both
Both can name the body's appetite for food as a picture of a person ruled by self-indulgence rather than by higher loyalties.Tit 1:12Rom 16:18Php 3:19
Almost every occurrence sits inside one fixed idiom, to have something in the belly, meaning a specific woman is pregnant at that moment in the story: Mary, the coming mothers warned about a coming disaster, and the woman clothed with the sun.Mat 1:18Mat 1:23Luk 1:31Mrk 13:17Rev 12:2
σπλάγχνονthe inward parts as the seat of deep compassion and affection, whereas this word's inner-self use is about the source of life rather than the feeling of pity
in nearly every New Testament use names not an organ but the warm compassion and affection a believer feels for others, especially fellow believers in needLuk 1:78Col 3:12Phm 1:7
Names the womb, the place a child is carried before birth, so it is the word that turns up in birth and pregnancy scenes.Luk 1:41Luk 1:42Jhn 3:4Gal 1:15
Names the stomach as the place food actually goes, which is why it shows up in arguments about eating, hunger, and what does or does not defile a person.Mat 15:17Mrk 7:19Luk 15:161Co 6:13
Stands for a person's appetite and inner drive, so it can be spoken of as the thing someone really serves or worships.Rom 16:18Php 3:19
Points to a hidden inner space that something can be inside of, whether a man swallowed by a sea creature or a scroll that turns bitter once it is eaten.Mat 12:40Rev 10:9Rev 10:10
Both
Both can speak of where a family line comes from, but from opposite sides: one is the mother who carries the child, the other is the father the line runs through.Luk 1:42Heb 7:5
Both name a broad region of the middle of the body rather than one exact organ, which is why English Bibles pick a different word for each scene, from "stomach" or "womb" for the one to "waist" or "loins" for the other.Mat 15:17Mat 3:4
Names the waist as the part of the body a belt goes around, so it appears whenever someone's clothing is described or tied up for work, travel, or battle.Mat 3:4Mrk 1:6Luk 12:35Eph 6:14
Belongs to a stock picture of readiness: gathering up a long robe at the waist so you can move fast, which is then applied to a mind braced for action.Luk 12:351Pe 1:13
Traces descent through the father, naming the man a family line comes out of, even for a descendant not yet born.Act 2:30Heb 7:5Heb 7:10
koilia in the other biblical languages
בֶּטֶןHebrew“belly: womb”the closest Hebrew match, carrying the very same double range of belly and womb
names the appetite that a person turns into their master, so that filling and pampering the stomach becomes the thing they truly serve and even worship in place of God.Php 3:19Rom 16:18
stands for the innermost self as a spring, the deep place out of which rivers of living water are promised to flow to the believer.Jhn 7:38
Both
both name the physical belly that food and swallowed things pass down into, the interior organ where what is eaten is received and felt.Ezk 3:3Mat 15:17
both name the mother's womb where a child is carried and out of which offspring come into the world.Gen 25:23Luk 1:41
both name the belly of the great sea creature that swallowed Jonah and held him inside for three days.Jon 1:17Mat 12:40
is the inward part felt as the seat of strong feeling, churning and aching with grief, longing, or tender mercy, and even used of God's own yearning compassion for his people.Jer 4:19Jer 31:20Isa 63:15Lam 1:20Sng 5:4
can be a man's own procreative interior, the place his seed and descendants are said to come out of, so a father's line issues from his body.Gen 15:42Sa 7:122Sa 16:11
What scholars say about koilia
The lexica (BDAG; LSJ) give κοιλία a cluster of related senses radiating from the abdominal cavity: the digestive organs (belly, stomach), the belly as the seat of physical appetite, the womb, and the innermost recesses of a person. Behm (TDNT 3:786-789) traces the last, figurative sense to Semitic usage in which the inward parts are the seat of the inner life, and it is this background that stands behind John 7:38. The Septuagint regularly uses κοιλία to render Hebrew beten, which shares the same belly/womb range, which fixed the double sense in Jewish Greek. The one genuinely contested point of interpretation is not the word's meaning but John 7:37-38, where the absence of ancient punctuation leaves it open whether the living water flows from the believer or from Christ.