Proto-Indo-European is the key to understanding why words like "mother" and "father" are so similar in so many different languages.
If you ever studied Latin or Greek word roots in your middle-school or high-school English classes, you may have wondered why English words are so different from Latin or Greek roots. For example, the Latin root for the word “tooth” is “dent-,” as in “dentist.” The Greek root is “odont-“ as in “orthodontist.” But the English word, of course, is “tooth.” Here's another one: The Latin root for “foot” is “ped-,” as in “pedestrian” or “pedestal.” The Greek root is “pod-,” as in “podiatrist.” But instead of a word containing P and D, English just has “foot.”
‘Mother’ and ‘Father’ Are Surprisingly Similar Between Some Languages
On the other hand, sometimes an English word is a lot like the equivalent root in Latin or Greek. For example, the Latin word for “mother” is “māter”; the Greek is “mētēr”; and they both resemble the English word, starting with M, with a T in the middle, and an R at the end.
What's going on with this mix of similarities and differences? The answer is that Latin, Greek, and English are all related, but Latin and Greek are more closely related to each other than they are to English. In fact, all three of these languages, and many others as well, are all part of a single language family, called the Indo-European languages, and they all ultimately trace back to a single, ancestral language, which was spoken centuries before writing was invented. We don’t know what speakers of that language called it, but today, it’s known as Proto-Indo-European.
How Do We Know Proto-Indo-European Existed?
A reasonable question is how we can possibly know that this language existed. To get an idea of how linguists reconstruct earlier forms of a language, let’s look at one of the major subfamilies within the Indo-European family: the Romance languages. These include the modern-day national languages of Portuguese, Spanish, French, Italian, and Romanian, as well as languages that don’t have a nation-state of their own, such as Occitan, and Catalan, which you may have been hearing about recently, as citizens of the Spanish region of Catalonia have pushed for independence.
These languages all developed from Latin, but let’s pretend for a moment that we don’t know that. We can still get a pretty good idea of what their ancestral language sounded like if we have enough words in the modern languages that we think might have a common origin. Let’s take the words for “mother” and “father” for example. In Portuguese, they’re “mãe” and “pai.” In Spanish and Italian, they’re “madre” and “padre.” In French, they’re “mère" and “père.”