WTN: fatal, lethal, mortal
James Harbeck
fatal, lethal, mortal
A couple of months ago, I read the following passage: “an extremely hazardous, quite possibly lethal sea journey.”
What was your first thought was reading that?
Mine was “Not lethal. Fatal.”
OK, but why?
If you ask someone to define fatal, they might say “deadly,” and if you ask them to define lethal, they might also say “deadly.” If you ask for another way of saying “deadly,” they might offer mortal.
If you want a more detailed definition, you may go to Merriam-Webster, which offers the following definitions:
· for fatal: “causing death”; “bringing ruin”; “causing failure”; “determining one’s fate”; “of or relating to fate”; “resembling fate in proceeding according to a fixed sequence”
· for lethal: “of, relating to, or causing death”; “capable of causing death”; “gravely damaging or destructive”; “very potent or effective” (in a more figurative sense)
· for mortal: “causing or having caused death: fatal”; “subject to death”; “of, relating to, or connected with death”; as well as several extended senses
OK, yeah, they all can mean ‘causing death’. And yet.
But of course we don’t learn the meanings of common words from the dictionary; we learn them from seeing the words in use, and occasionally, when we’re young, from having someone define the word for us, usually with a synonym. And then we see how they’re used.
We know, for instance, that you can receive a fatal wound from a lethal weapon in mortal combat, and maybe you can receive a mortal wound from a fatal weapon in lethal combat (or maybe not), but you wouldn’t receive a lethal wound from a mortal weapon in fatal combat. Somehow that doesn’t sound exactly right.
Words are known by the company they keep. So what company do these words keep? When I look at the Corpus of Contemporary American English and search for collocations, I find that the following are the top dozen words that come right after each of these:
· for fatal: shooting, flaw, disease, attraction, mistake, accident, blow, accidents, crash, heart, crashes, error
· for lethal: injection, weapon, force, dose, weapons, combination, injections, doses, drugs, violence, form, virus
· for mortal: sin, Kombat, danger, enemy, man, enemies, life, coil, Wkly, world, men, threat
(You probably know what Kombat is doing there – Mortal Kombat is a popular game series. As to Wkly, Morb Mortal Wkly Rep is the citation abbreviation for the medical journal Morbidity and Mortality Weekly Report. So it’s kind of an interloper. To make up for that, the 13th word in the list is combat.)
To get more real-life insight, I asked people on Bluesky: “According to you (as in from your own mind, not from a dictionary), what is the difference between ‘lethal’ and ‘fatal’? Take your time. Consider instances where you could use one but perhaps not the other.” (I didn’t ask about mortal because at first I was just thinking about those two.) Here are some of the responses I got:
i feel like "lethal" is done to somebody, and "fatal" just happens. a disease is fatal, not lethal. an accidental self-administered drug overdose is fatal. if the fault of a doctor, they administered a lethal dose. a weapon attack is lethal, an accident is fatal.
Lethal has the potential for death - like a weapon; fatal suggests that death is assured, like an attraction.
Hmmm this sounds weird but: fatal is always what you say about something in the past. Like, the fatal blow is only talked about after a person is assuredly dead. Lethal feel more about potential. This is probably miles off.
Result? Timing? Lethal has 'potential', while 'Fatal' describes sometime that's already happened and has definitely ended in death.
Broadly, "fatal" is about "fate" and so emphasises the result, not cause or intent, and often implies inevitability (fatal flaw). "Lethal" implies intent or design (though it may not imply will: a lethal venom is evolved). Of course, such distinctions are pretty fluid and subjective.
I have no idea why, but lethal sounds active. Fatal sounds more passive. Like, lethal is something one does. Fatal is just something that happens. Makes no sense except in my head.🤷♀️
To a first approximation, I think I’m more likely to use “lethal” to describe physical objects/substances, and “fatal” to describe events.
Off the top of my head, "lethal" can be adjectival in an abstract way, and carries a sense of "able to cause death." "Fatal" has more certainty to it. "The third dose of heroin she took was fatal." This is not definitive, rather, it's how the nuance strikes me, and they overlap in various cases.
Lethal is a possibility. Fatal is a result.
So, then. Here is what I get from all that:
Fatal has a sense of inevitability to it: if it’s about death, it’s unavoidable; if it’s more figurative, such as “a fatal error” or (for a computer) “a fatal exception,” it is still irreversible. Like the hand of fate.
Lethal has a sense of purpose or potential: a lethal dose may remain unadministered, but a fatal dose already has been administered. A lethal weapon can kill you, but that doesn’t mean it will, let alone already has.
And mortal puts a thing in the atmosphere of death: a mortal enemy is someone who wants to kill you, or vice versa; mortal combat might or might not guarantee death but definitely allows for it; in this mortal world we mortal beings must ultimately shuffle off this mortal coil.
All of which, if you look at the origins and histories of these words, makes sense.
Fatal is, by origin, ‘of or relating to fate’; it comes from Latin fatalis, from fatum, which means ‘fate’ or ‘destiny’, of course, but comes from a verb meaning ‘speak’: it is the word that is spoken, the prophecy, the edict, the divine utterance. It has been in English since the later 1300s and first meant ‘decreed by destiny’. It always comes with the echoes of “fate.”
Lethal is, by origin, ‘deadly’; it comes from Latin letalis, with an intrusive h that chance and confusion ordained should be there – it’s a misconjecture of an origin in Ancient Greek λήθη lḗthē, ‘oblivion, forgetfulness’. Letaliscomes from letum, ‘violent death’, ‘killing’, ‘ruin’; its further etymology is uncertain. It has been in English since the early 1600s and first meant (as it still means), per Oxford, “that may or will cause death.” It doesn’t come with strong echoes of other words.
Mortal is, by origin, ‘involving death’, as in ‘susceptible to death’ (i.e., not immortal), or ‘causing death’, or ‘punishable by death’, or ‘relating to the time of death’; it comes from Latin mortalis, from mors, ‘death’, which in turn traces back to a Proto-Indo-European root also referring to death that has given rise to deathly words involving /m/ and /r/ and usually /s/ or /t/ in quite a few languages. It has been in English since the later 1300s and was first used in relation to battle, combat, et cetera, as in mortal foe (one who will be satisfied only by the death of their enemy) and mortal battle and of course mortal combat (fought to the death). It brings a lot of associative baggage with it, since mortal has such a wide usefulness for human things, and it also echoes many other related morbid mor- words.
So there it is: three kinds of -talis – fa, le, mor. In matters of killing, fa will, le can, mor can’t not. We all have a sense of how to use these words, and how not to, but we mostly just feel our way around them. And meanwhile, we still also have the Anglo-Saxon words that these three Latin imports have not completely supplanted: deadly and deathly.
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