Students understanding the complexity of language

Chapter 15.5 PIE Morphology


The basic morphemic structure of PIE has many similarities with Modern English: a root morpheme to which is added various derivational and then inflectional morphemes. The major difference is the productive use of what we call ablaut or gradation, a technique the traces of which are still found in Modern English, though no longer in productive use. Ablaut is a regular system of vowel variation, as seen in the Modern English root sing. If we change the vowel of this verb we produce other grammatical forms, though the semantic meaning remains the same: the present tense has one "grade" of the vowel, which appears as sing, while the past tense has a different grade, and appears as sang. The past participle originally had a zero-grade, that is, no vowel at all, and appears in Modern English as sung. Finally, there is a noun version which originally had yet another grade. This appears now as song. Throughout all the vowel grades, the basic form of the word has remained as S_NG. We therefore can represent the basic structure of a PIE morpheme as CVC (consonant-vowel-consonant), with the understanding that the internal vowel can change.

The PIE ablaut series alternates between an e-grade (the origin of sing) or an o-grade (the origin of song) or a zero-grade (∅-grade) (the origin of sung) if there is no vowel. There can also be grades with lengthened versions of the vowels: an ē-grade and an ō-grade (the origin of song).

An example from PIE is the root morpheme *wed-, which means “wet.” This morpheme has many descendents in Modern English, each of which looks very different today depending on which vowel grade of the root was used or which derivational suffixes were added to it. The root can appear in an e-grade as *wed-, a lengthened ē-grade as *wēd-, or it can appear with an /o/ vowel, as *wod- or *wōd-; it can also appear with in zero-grade as *wd-. The problem with this form is there is no vowel, so the semivowel /w/ converts to the vocalic form /u/, and the root becomes *ud-. The following list presents Modern English words based on different variations of the root *wed- from PIE:

  • o-grade with the noun suffix –r: *wod-r-. This is Modern English water, a noun formed from the adjective of being wet, meaning "the thing that is wet."
  • o-grade with a reflexive suffix –sk- (meaning “to do to oneself”) and a verb suffix, turning the adjective into a verb. In Germanic this appears as *wat-sk-anan, "to make oneself wet." This becomes Old English wascan, Modern English, “wash.”
  • zero-grade with a noun suffix relating to animals: *ud-ro- or *ud-ra-. This becomes udra in Greek (Modern English hydra) and in Germanic it becomes otor (Modern English otter). Both otters and hydras are etymologically “water animals.”
  • e-grade with a nasal infix -n- *we-n-d-, with the Proto-Germanic suffix *-ruz added to get Proto-Germanic *wintruz, “the wet time of year,” Modern English "winter."
  • zero-grade with a nasal infix and a noun suffix: *u-n-d-a-, becomes Latin unda, “wave” (compare Modern English words like undulate, “to act like a wave.”)
  • zero grade with the suffix –skio: *udskio- becomes Old Irish uisce, Modern English whisky.
  • o-grade with the suffix noun –a: *wod-a-. Becomes Russian voda, “water” or with the diminutive suffix –ka, vodka, “little water, i.e. vodka.”

In sum, PIE morphology worked in very much the same way as Modern English, and all other descendents of PIE. Root morphemes can appear with different grades of vowels and derivational suffixes can be added to them to create new meanings. As such, these languages are quite different from agglutinative languages like Finnish, Japanese, or Nahuatl, which add strings of unchanged morphemes together.

PIE Inflectional Endings

PIE also had inflectional suffixes that were added to morphemes to give grammatical information. Different functions of a noun within a sentence each take a different inflectional ending. These functions are called cases. Modern English nouns have two basic cases. Subject/object and possessive. Consider the two sentences:

  1. The boy carried a book.
  2. The boy’s books were heavy.

If we look at the first sentence, we see that the words boy and book have no inflectional endings, even though one is the subject of the sentence and the other is the object of the sentence. If we look at the second sentence, we see that boy’s has the inflectional ending –‘s to signify that it is in the possessive case, and books has the inflectional ending -s to signify a plural. These are the only case endings that remain in Modern English for nouns.

Pronouns in Modern English preserve three cases: subject, object and possessive.

  1. I saw the boy.
  2. The boy saw me.
  3. The boy saw my book.

In addition to the first person pronouns above, we have he, his and him; we, our, and us; they, their, and them, and so on. Some pronouns, however, only preserve two distinct forms: she and her; you and your.

Modern English also preserves two numbers, singular and plural. In most nouns, the plural inflectional ending is s. Pronouns also preserve a distinction in number, with I and we and he, she, it and they.

PIE had eight different cases, each with a distinct inflectional ending. It also distinguished between singular and plural and also dual, indicating that there were two of an object. Thus, a single noun could have up to 24 different inflectional endings depending on which case it was and whether it was singular, dual or plural. In fact, it had far more than these 24 endings, for different nouns took different kinds of endings. We still have some remnants of this in Modern English. Our usual plural suffix is –s, but we also have –en as in oxen and brethren. We also have a zero-ending as in deer or sheep (i.e., people do not say *deers or *sheeps). If we add to those the plural inflectional endings from foreign languages like Latin (cactus, cacti) and Greek (phenomenon, phenomena), and so on, you will see that English is not as simple in its inflectional endings as it at first appears.

Let’s look at the PIE root morpheme *eku-. This is probably related to the adjective *ōku “swift” (which has a lengthened o-grade). If we add a basic noun suffix *-o onto the end of *eku-, we get the noun *ekw-o-, which would mean “a thing that is swift.” This is the origin of Latin equus, “horse,” from which we get Modern English terms like equine, equestrian, etc. To put this noun into a sentence, we must add inflectional endings to the root *ekwo-. If it is the subject of the sentence, we add *–s, making *ekwos (Latin equus). If it is the direct object of the sentence, we add *–m, making *ekwom (Latin equum). If it is possessive, we add *-syo, making *ekwosyo. Other forms are *ekwobhyos, *ekwod, *ekwoysu, and so on.

In Modern English verbs, we have one distinct ending in the present tense, for the 3rd person singular, and we also have a past tense inflectional ending, -ed. Many modern languages have different inflectional endings for 1st, 2nd, and 3rd person, both singular and plural. PIE had inflectional endings for all these and in numerous different tenses and aspects (While tenses govern time, such as future, present, and past, aspect governs the way in which the action was completed: a habitual action, a completed action, an action that represents an eternal state, and so on).

In conclusion, PIE had a vast number of inflectional endings, not only far more than Modern English, but more than one finds even in languages like ancient Greek or Sanskrit. As PIE evolved throughout the millennia, it has lost many of these endings, simplifying them into fewer and fewer cases or tenses.


Because Modern English has lost case endings to signify the grammatical function of nouns, we must rely heavily on word order (syntax) to make our sentences clear. In the sentence “the cowboy rode the horse,” we know "the cowboy" is the subject of the sentence because it comes before the verb and we know "the horse" is the direct object because it comes after the verb. If we reversed the order, “The horse rode the cowboy,” we get a sentence that means something entirely different. Languages that rely heavily on word order are called analytic languages. PIE on the other hand does not need to rely on word order. It would not matter where *ekwos appeared in a sentence in PIE because the final –s tells us that it is the subject of the sentence. Similarly, even if the word *ekwom appeared as the first word of an utterance in PIE, speakers would recognize it as the direct object because of the final –m. Languages that rely heavily on inflectional suffixes to signify grammatical structure are called synthetic. We will see in the next few weeks how English has changed over the last 1000 years from a highly synthetic language to a highly analytic language.

Because of the inflectional endings, a language like PIE could be completely free in its word order. We still see this today in languages that are heavily synthetic. Latin, for example, has a very free word order. Linguists have determined, however, that although PIE could have used fairly free word order, it is most likely that PIE speakers preferred to put the verb last. Thus, they would have the subject of the sentence first, the direct object next, and the verb last. This makes what we call an SOV (subject-object-verb) word order, or more simply an OV word order. English, on the other hand, is an SVO language, or more simply, a VO language. Further details of PIE syntax are beyond the scope of this course, but you can read much more about it in this online edition of Winfred Lehmann's Proto-Indo-European Syntax.