While working in class, I came across this. They have a similar spelling, yet mean completely different things. Is this just random or does it have an actual purpose in the Latin language?

  • Book = Libri
  • Children = Liberi

1 Answer 1


These words are unrelated: they developed independently from different Proto-Indo-European roots, according to Michiel de Vaan's Etymological Dictionary (337–38).

First, liber or librī, meaning "book," is thought to come from a PIE word meaning "leaf, rind": *lubʰ-ro-. De Vaan cites several Indo-European languages that have attested cognates and summarizes:

We may surmise that liber is cognate with *lubʰ- and goes back to a PIE word or a European word 'leaf, rind'.

On the other hand, līber, meaning "children," comes from a different PIE word (*h1leudʰ-ero-), through a Proto-Italic word *leuþ-ero. The word also means "free," and the "children" meaning developed later. De Vaan explains again:

The change of the pl. līberī to 'children' is explained by Benveniste from legal terminology, in which the legitimate 'children' of a free couple were denominated as 'free ones'.

So it's simply a coincidence that these words ultimately came to look very similar: they developed from distinct PIE roots.

  • 2
    It's also worth noting that the parent speech provenance reflects in the short i in lĭber the child (u > proto-Italic *i) but long *i in līber the book (from the diphthong *eu > *ī). These were simply two different sounds for a pre-classical and classical Latin speaker, not quite as similar as they are to the modern ear! Commented Jul 28, 2016 at 4:37
  • 1
    And it is almost worth noting that the English have always been famous for teaching wrong quantities. With the result that Liber (book) with a short i gives us Library with a long i. But Līber (free/child) with a long ee sound gives English 'liberty' with short i
    – Hugh
    Commented Jun 28, 2017 at 4:48
  • 1
    @kkm. It is actually the other way around. "Child" has a long i, "book" has a short i.
    – fdb
    Commented Aug 17, 2017 at 22:57
  • @fdb Better later than never. Thanks, of course I switched them around. Commented Sep 19, 2017 at 7:14

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