/mɔːrˈtælɪti/
[noun] The fact that all living things must die at some point. It can also refer to the number of deaths in a particular place or time period.
Every time you say 'mortality', you are using the same root word that Romans used for 'murder' — both come from mors, simply meaning death.
At the heart of 'mortality' sits the Latin word mors, meaning 'death'. This ancient root is one of the oldest and most travelled words in the Indo-European family, stretching back to the Proto-Indo-European root *mer-, which carried the sense of dying or ceasing to exist. From mors, Latin built the adjective mortalis, meaning 'subject to death' or 'capable of dying', which then became the abstract noun mortalitas, meaning 'the condition of being mortal' — the state of being something that must eventually die. It was this form, mortalitas, that passed through Old French as mortalité before arriving in Middle English as 'mortality' in the 14th century.
The word entered English during a period when death was very much at the front of people's minds. The 14th century was the era of the Black Death, the devastating plague that wiped out perhaps a third of Europe's population. Writers and thinkers of the time reached instinctively for words that could frame the overwhelming scale of dying around them, and 'mortality' — with its grand, philosophical weight — served that need perfectly. It gave death a name that felt less personal and more universal, turning individual loss into a shared human condition.
What makes this word's family tree so remarkable is just how many common English words grew from the same Latin root mors. The adjective mortalis gave us 'mortal' directly. The Latin phrase mortalis inimicus, meaning a deadly enemy, eventually shaped the idea behind 'mortal enemy'. The Latin verb mortificare, meaning to cause death or to deaden, travelled through Old French as mortifier before becoming English 'mortify' — though over time its meaning softened from literal killing to a feeling of deep embarrassment, as if one wished to die of shame. Similarly, the Latin amortizare, meaning to kill off a debt, passed through Anglo-French amortiss- into English 'amortize', used today in finance to describe paying off a loan gradually.
The same Proto-Indo-European root *mer- also branched in another direction, flowing into ancient Greek as the word brotos, meaning 'mortal man'. Greek mythology wrapped this idea into the figure of the ambrosia-eating gods: the prefix a- meaning 'not', combined with brotos, gave the Greeks ambrotos, meaning 'immortal', which in turn gave English the word 'ambrosia' — the food of the gods that kept them forever alive. So when you eat ambrosia salad at a summer picnic, you are, in a small linguistic way, eating the food of immortality.
Over the centuries, 'mortality' has carried two distinct but related meanings that both remain in use today. The first is philosophical and personal: the awareness that you, as a human being, will one day die. This is the 'mortality' that poets write about, the one that makes sunsets feel more beautiful because they are temporary. The second meaning is statistical and public: the mortality rate of a disease, a war, or a famine — how many people died, measured and counted. Both senses share the same honest core. Whether we are speaking of one life or millions, 'mortality' insists on the same plain truth: that everything which lives must also end.