rachi- or rachio- [from Greek rachis spine] Spine (rachiodont).

radio- [from Latin radius ray] (1) denotes radioactivity or radiant energy (radiograph, radioisotope); (2) pertaining to the radius (radiohumeral).

re- [Latin re- again] Back, again (resuscitation).

reni- or reno- [from Latin renunculus kidney] Denotes kidney (renogastric).

reti- or reticul- or reticulo- [from Latin rete, retis net, snare] Denotes a network or rete (retiform, reticulocytosis).

retin- or retino- [from Latin rete, retis net; refering to the network of vessels on the retina] Denotes the retina (retinopathy).

retro- [Latin retro backwards, to the rear, behind, on the back; back in time, formerly] (1) backward (retroserrulate);(2) situated behind (retroocular); (3) reversing a trend (retroversion).

rhabd- or rhabdo- [from Greek rhabdos rod, stick] Denotes a rod or stick; rod-shaped (rhabdomyoma).

rheo- [from Greek rheos current] Flow, stream, current, electric current (rheostat).

rhiz- or rhizo- [from Greek rhiza root] Root (rhizanthous).

sacchar- or saccharo- [from Greek sakcharon sugar] Sugar (saccharuria).

sacr- or sacra- or sacro- [from Latin sacrum sacrum] Denotes the sacrum (sacroiliac, sacrolumbar).

salping- or salpingo- [from Greek salpinx tube] Relating to a salpinx, especially a eustachian or fallopian tube (salpingitis, salpingotomy).

sangui- [from Latin sanguis blood] Denotes blood (sanguiferous).

sapr- or sapro- [from Greek sapros rotten] Rotten, putrid, dead, decaying (saprophyte).

sarc- or sarco- [from Greek sarx flesh] Flesh, soft tissue (sarcoma, sarcomere).

saur- or sauro- [from Greek saura lizard] Lizard, lizardlike (saurian, saurophagus, sauropod).

schiz- or schizo- [from Greek schizein to split or cleave] Split, cleft, divided; produced by cleavage (schizocoel).

scler- or sclero- [from Greek skleros hard] (1) hard (scleriasis, scleroderma); (2) relating to the sclera (sclerocornea).

scolec- or scoleco- [from Greek skolex worm] Worm (scolecoid).

semi- [from Latin semi half] Half (semilunar).

sept- or septi- [from Latin septem seven] Seven (septifolious).

sept- or septi- or septo- [from Latin separare to separate] Septum (septectomy).

sept- or septi- or septic- septico- [from Greek sepsis putrefaction] Sepsis (septicemia).

sesqui- [from Latin sesqui one and a half times] One and a half (sesquidiploid).

sex- or sexi- or sexti- [from Latin sex, sextus six] Six (sextuplet, sextipara).

sial- or sialo- [from Greek sialon saliva] Saliva (sialagogue)

sider- or sidero- [from Greek sideros iron] Denotes iron or steel (siderocytes)

sinistr- or sinistro- [from Latin sinister, sinistra left] Left, to the left (sinistrocardia).

sito- [from Greek sitos grain] (1) grain (Sitophilus, sitosterol); (2) food (sitology).

som- or soma- or somato- [from Greek soma body] Body, of the body (somatic, somites).

speci- or specie- or specio- [from Latin species appearance] Species.

spectr- or spectro- [New Latin spectrum spectrum] (1) of or pertaining to spectra (spectral karyotype); (2) of or pertaining to a spectrophotometer.

sperm- or sperma- or spermi- or spermo- or spermat- or spermato- [from Greek sperma seed, semen, race, origin] Denotes seed, sperm, germ, semen (spermatid).

sphen- or spheno- [from Greek sphen wedge] (1) wedge, wedge-shaped (Sphenisciformes); (2) of or pertaining to the sphenoid. PICTURE OF SPHENOID

sphygm- or sphygmo- [from Greek sphygmos pulse] Denotes the pulse (sphygmic).

spir- or spiri- or spiro- [from Greek speira coil] Coil, spiral (Spirillum).

spiro- [from Latin spirare to breathe; blow; live] Respiration (spiroscope).

splanchn- or splanchno- [from Greek splangchnon internal organ] Denotes internal organs (splanchnology).

spondyl- or spondylo- [from Greek spondylos a vertebra] Pertaining to vertebra(e) (spondylitis).

spor- or spori- or sporo- [from Greek sporos sowing, seed, offspring, semen] Seed, spore (sporulation).

squam- or squamo- [from Latin squama scale] Scale, scalelike (Squamata).

staphyl- or staphylo- [from Greek staphyle bunch of grapes] (1) like a bunch of grapes (Staphylococcus); (2) relating to the uvula or soft palate (staphylopharyngeus); (3) relating to Staphylococcus (staphyloangina, staphylococcemia).

stat- or stato- [from Greek statos standing] Standing, resting, balanced (statocyst).

steat- or steato- [from Greek stear fat, tallow] Fat (steatorrhea).

sten- or steno- [from Greek stenos narrow] Narrow, contracted, short (stenosis, stenostomia, stenothermal).

sterc- or sterco- [from Latin stercus dung] Denotes excrement (stercoral).

stere- or stereo- [from Greek stereos solid] Solid (stereochemistry).

steth- or stetho- [from Greek stethos chest] Denotes the chest (stethoscope).

stomat- or stomato- [from Greek stoma, stomat- mouth] Mouth, opening, stoma (Stomatidae, stomatologist).

strat- or strato- [from Latin stratum bed, blanket] Stratum (stratified, stratigraphy).

strept- or strepto- [from Greek streptos to be bent or turned] (1) twisted (streptococcus); (2) streptococcus caused or related (strepticemia, streptodermatitis).

styl- or stylo- [from Greek stylos pillar] Pertaining to the styloid process (stylomandibular).

sub- [Latin sub under, beneath, behind, during] (1) under (subcutaneous); (2) a division of taxonomic group (suborder).

sulf- or sulfo- (British spelling is sulph-) [Latin sulfur brimstone, sulfur] Indicates presence of sulfur (sulfonamides).

super- or supra- [Latin super above, on top, upon, over, upwards] Above, over, upon (suprarenal, superorder).

sym- or syn- [from Greek syn together] (1) with, together, united (symbiosis, synapsis, syncytium, syngamy); (2) the same (syngeneic).

syphil- or syphilo- [derivation uncertain] Syphilis (syphilomania).

syring- or syringo- [from Greek syrinx pipe or tube] Tube, fistula, duct, canal (syringitis).