Hex words with only letters (a to f) in English from https://www.dictionary.com/:
- a
- aa (basaltic lava having a rough surface)
- be
- ea (the Akkadian god of wisdom, the son of Apsu and father of Marduk: the counterpart of Enki)
- fa (the syllable used for the fourth tone of a diatonic scale)
- aba (a coarse, felted fabric woven of camel's or goat's hair)
- abb (low-grade wool from the breech or outer edges of a fleece)
- ace
- ate
- baa (to make the sound of a sheep; bleat)
- bad
- bae (an affectionate term used to address or refer to one’s girlfriend, boyfriend, spouse, etc.)
- bed
- bee
- cab (a taxicab)
- cad (an ill-bred man, especially one who behaves in a dishonorable or irresponsible way toward women)
- dad
- dee (a metal loop attached to tack, for fastening gear)
- ebb (the flowing back of the tide as the water returns to the sea)
- fab (fabulous)
- fad
- fed
- fee
- baba (a spongelike cake leavened with yeast and often containing raisins, baked in a small mold and then usually soaked with a rum syrup)
- babe
- bade (a simple past tense of bid)
- bead
- beef
- boob
- cade (a juniper, Juniperus oxycedrus, of the Mediterranean area)
- cafe
- dada (the style and techniques of a group of artists, writers, etc., of the early 20th century who exploited accidental and incongruous effects in their work and who programmatically challenged established canons of art, thought, morality, etc)
- dead
- deaf
- deb (a debutante)
- dece (great, wonderful)
- deed
- ecad (an organism whose form has been affected by its environment)
- face
- fade
- feed
- food
- abaca (a Philippine plant, Musa textilis)
- faced
- faded
- facade
- facebooc (IPv6 addresses of www.facebook.com)