faci- or facio- [from Latin facies face] Denotes the face (faciocervical, faciolingual, facioplasty).

fauc- [from Latin fauces pharynx] Denotes the fauces (faucitis).

febri- [from Latin febris fever] Fever (febricity, febrifuge, febrile).

feli- [from Latin felis cat] Cat (Felidae).

femto- [from Danish femten fifteen] 10^-15 (femtoliter).

ferr- or ferre- or ferro- [from Latin ferrum iron] Containing iron (ferredoxin).

feti- or feto- or foeti- or foeto- [from Latin fetus offsping, young] Denotes the fetus (fetotoxic).

fibulo- [from Latin fibula clasp, brooch] Of or pertaining to the fibula (fibulocalcaneal).

fil- or fili- [from Latin filum thread] Denotes filament(s), thread(s) or something threadlike (filiferous, filiform).

filic- [from Latin filix, filicis fern, bracken] Pertaining to ferns; used in taxonomy (filicifolium).

flav- or flavo- [from Latin flavus yellow, golden] Yellow, golden (flavobacteria).

fluor- or fluori- or fluoro- [from fluorine] (1) fluorine (2) fluorescent.

fore- [from Old English fore- earlier, in front] Before, front, in front of; often used in English names of body parts (foreleg, forearm, forehead, foreskin).

front- or fronto- [from Latin frons, frontis forehead, face, front, fore part] (1) anterior (frontal lobe); (2) of or pertaining to the forehead or frontal bone (frontoparietal).

galact- or galacto- [from Greek gala, galact- milk] Milk (galactose).

gam- or gamo- [from Greek gamia marriage] (1) united, joined (gamopetalous, gamophyllous); (2) sexual, sexually (gamete, gamone).

gamet- or gameto- [from Greek gamia marriage] Gamete (gametangium).

gaster- or gastr- or gastro- [from Greek gaster belly] Stomach, belly (gastroenteritis, Gastropoda, gastroenteritis, gastric, gastrolith).

gen- or geno- [from Greek gennan to produce] Gene (genotype).

genu- [from Latin genu knee] Denotes the knee (genucubital).

giga- [prefix in International System of Units] billion (10⁹) (gigabase).

gingiv- or gingivo- [from Latin gingivae gums] Denotes the gums (gingivoglossitis).

glauc- or glauco- [from Latin glaucus bluish gray] (1) pale yellow-green (2) light bluish gray (Glaucium, glaucoma).

gloss- or glosso- [from Greek glossa tongue] Relating to the tongue (glossalgia, glossodynia).

glott- or glotto- [from Greek glottis, glossa tongue] (1) pertaining to the glottis; (2) pertaining to the tongue (glottitis).

glyc- or glyco- [from Greek glykys sweet] In the names of compounds, indicates the the presence of glycerine or a like substance (glyceride).

gnath- or gnatho- [from Greek genys jaw, cheek] Denotes jaw (gnathochilarium).

gon- or gono- [from Greek gonos genitals, seed, offspring, procreation] (1) sexual (gonads, gonorrhea); (2) generative; (3) semen (gonopoietic, gonium).

gymn- or gymno- [from Greek gymnos naked] Naked, uncovered (gymnosperm, gymnophobia).

gyn- or gyno- or gynec- or gyneco- (British spellings: gynaec-, gynaeco-) [from Greek gyne woman] Woman, relating to women (gynecology); (2) female reproductive organ: ovary, pistil (gynoecium)