In this lesson: Master Greek log/logue (word, reason) — the root GRE uses for words about words and reasoning about reasoning.
About This Root
The root log comes from one of the richest words in Greek: logos (λόγος). For the Greeks, logos was never just a single idea. It meant the word you speak, the speech you give, the account you offer, and — crucially — the reason or rational principle behind things. To say something in logos was to put thought into ordered speech. This double life — speech on one side, reason on the other — is why log powers two very different families of English words.
Family one: speech and what is spoken. Here logos keeps its plain meaning of "word" or "talk," and Greek prefixes tell you the shape of that talk:
- dia- (across, between) + logos → dialogue: words passing between two sides — a conversation.
- mono- (one) + logos → monologue: one person holding the floor with a long single speech.
- pro- (before) + logos → prologue: the words spoken before the main work begins.
- epi- (upon, after) + logos → epilogue: the words added after the story ends.
- ana- (according to, in proportion) + logos → analogy: reasoning that two things stand in the same proportion — "A is to B as C is to D."
- apo- (away, back) + logos → apology: originally a speech given in your own defense, talking your way back from an accusation. (That older sense survives in "an apology for one's beliefs.")
- eu- (good) + logos → eulogy: good words spoken about someone, especially the dead.
- neo- (new) + logos → neologism: a newly coined word.
Family two: the study of something — the suffix -logy. This is the other, more famous side of logos: "reasoned account of," hence "the systematic study of." Attach -logy to a subject and you name an entire field. The pattern is almost mechanical: X + logos = the study of X, X + logist = the person who studies X, X + logical = relating to that study:
- bio- (life) → biology (study of life), biologist, biological
- psych- (mind) → psychology, psychologist, psychological
- eco- (household, environment) → ecology, ecologist, ecological
- theo- (god) → theology, theological
- gen- (birth, descent) → genealogy (the account of one's lineage)
- astro- (star) → astrology → astrological
- arch(aeo)- (ancient) → archaeology → archaeological
- chrono- (time) → chronology → chronological
- anthropo- (human) → anthropologist
- path- (suffering, disease) → pathology → pathological
Once you see this template, dozens of intimidating academic words decode themselves: meteorology is the study of "things in the air," cardiology the study of the heart, dermatology the study of skin, herpetology the study of reptiles. You don't memorize them — you read them.
A warning about look-alikes. Not every log in English is logos. The plain English word log (a piece of cut wood, and from there a ship's logbook and any record) is Germanic and has nothing to do with Greek speech. Logistics (supply and movement of goods) comes from French loger, "to lodge / quarter troops" — also unrelated. And rhapsody ends in -ody (ōidē, "song"), not -logy. They look like family but married in from elsewhere.
Two faces of one word. When log means talking, think dia-LOGUE — words bouncing between two people. When it's the suffix -logy, just read it as "the study of": bio-logy = study of life, eco-logy = study of the home/environment. X + logy = the science of X; X + logist = the person who does it.
Focus words· 8
ana- (according to, in proportion) + logy (logos here = ratio) = 'matching proportion.' The Greeks used analogia for A:B = C:D. So an analogy claims two unlike things share the same relationship, not just a loose resemblance.
Hides a math idea. ana- (according to, in proportion) + logos (here 'ratio, proportion') = 'matching ratio.' The Greeks used analogia for proportions: A:B as C:D. An analogy says two unlike things share the same relationship — 'a CPU is to a computer as a brain is to a body.' So an analogy isn't just any comparison; it claims a parallel structure.
He drew an analogy between the brain and a computer.
The teacher used a cooking analogy to explain chemistry.
The adjective of analogy: ana- (in proportion) + log (ratio) + -ous (having the quality of) = standing in a comparable relationship. Usually followed by 'to': X is analogous to Y.
The wings of a bird are analogous to the arms of a human.
Their situation is analogous to ours a decade ago.
eu- (good) + logy (logos = words) = 'good words.' A eulogy is the praise spoken about someone, classically over the dead at a funeral. Spelling trap: eu-LOG-y, unrelated to 'allergy.'
eu- (good) + logos (words) = 'good words.' A eulogy is the speech of praise given about someone, classically at a funeral — you say good words over the departed. Note the spelling trap: eu-LOG-y, not the unrelated 'allergy.' The verb eulogize means to deliver or perform such praise (it is a verb, not a noun).
She delivered a moving eulogy at her father's funeral.
The article read more like a eulogy than a review.
In monologue and analogy, the Greek root log means…
neo (neos = new) + log (logos = word) + -ism = literally "new-word-ism": a freshly invented term. Every word was a neologism once — selfie, podcast, doomscrolling all started as new coinages before settling into everyday use.
The word carries a faint judgment. Calling a term a neologism can be neutral ("a useful new coinage") or mildly dismissive ("a made-up word that hasn't earned its place"). The same coinage can be celebrated by some and rolled-eyed at by others — the label itself stays neutral; the tone comes from the speaker.
'Selfie' was once a neologism but is now in every dictionary.
The internet generates neologisms faster than dictionaries can track them.
mono- (one) + -logue (Greek logos, 'speech') = one person's speech. The opposite of dialogue (dia- 'between' + logos): instead of two voices going back and forth, a single voice holds the floor.
The actor delivered a powerful five-minute monologue.
His apology turned into a self-pitying monologue.
pro- (before) + logue (logos = speech) = the words spoken before the main work begins. Figuratively, any event that sets the stage for what follows.
The novel opens with a short prologue set in 1920.
The protests were a prologue to the revolution.
eu- (good) + logy (words) → "good words spoken of someone — at a funeral." Which word?
epi- (upon, after) + logue (logos = speech) = the words added after the story ends. The mirror image of prologue.
An epilogue tells us what happened to the characters years later.
She added a brief epilogue thanking her readers.
etymo (Greek etumon = the true sense of a word) + logy (study) = the study of a word's 'true,' original meaning — tracing where words come from. This very entry is etymology in action.
The etymology of 'salary' traces back to Roman salt rations.
She loves looking up the etymology of strange words.
Extended family · 40 words
See the root page for the full family.
Don't confuse
Latin loqu is the act of speaking; Greek log is the word or the logic itself. loquacious describes a talker; analogous describes a relationship of reason. And -logy = "the study of" (etymology: the study of a word's true origin).
Related Roots
Both touch on 'speech/sound,' but log (logos) is about meaningful words and reasoning — dialogue, logic — while phon (Greek phōnē) is the raw sound or voice itself — telephone, phonetics. Meaning and reason → log; sound waves → phon.
Both name fields and forms of expression, but log = the spoken word / reasoned study (-logy = study of), while graph = the written or drawn record (-graphy = writing/recording of). geo-logy studies the earth; geo-graphy writes/maps it. Study → -logy; writing → -graphy.
Both involve speaking. dict (Latin dicere, 'to say') stresses the act of pronouncing/declaring — dictate, predict, verdict. log stresses the words as meaning and reason — dialogue, logic. Saying out loud → dict; reasoned discourse → log.
Practice
What does the Greek root log/logue/logy mean?