Morphology: How Words Are Built

The word unbreakableness has never been in a dictionary, because nobody needs to look it up. You can see how it works: break is the root, -able turns it into "capable of being broken", un- reverses that, and -ness makes the result a thing you can talk about. Four pieces, each with its own job, snapped together by a rule you absorbed as a child and never wrote down.

Now take the Turkish word evlerinizden. It is one word, and it means "from your houses" (you plural). It is also four pieces: ev "house", -ler plural, -iniz "your", -den "from". Chinese would use separate words for most of that; Inuktitut and Yup'ik would pack in a whole sentence. How much goes inside the word, and how it is bolted on, is what morphology describes.

Morphemes: the smallest pieces that carry meaning

A morpheme is the smallest unit that pairs a form with a meaning or a grammatical job. It is not the same as a syllable (the word cats has one syllable and two morphemes) and not the same as a word (unbreakableness has four). Some morphemes can stand alone and are called free (break); some must attach and are bound (-able, -ness). The core of a word is its root; what attaches is an affix.

To compare languages, linguists write examples in a standard way, the Leipzig Glossing Rules: the word in the language with hyphens at the morpheme boundaries, a line below it giving a gloss for each piece (small capitals or abbreviations for grammatical ones, such as PL for plural, 1SG for "I"), and a free translation. The tool below lets you cut nine words, from every inhabited continent, along their seams.

Roots, affixes and patterns: three ways to build

Most people picture a word as a root with things stuck to its ends, and that is the commonest method: suffixing (English -ness, Turkish -ler) is more frequent in the world's languages than prefixing (Swahili ni- "I", English un-). But there are other options. Infixing puts the piece inside: in Tagalog (the Philippines), sulat "write" becomes sumulat, with -um- marking the actor. Circumfixing wraps both sides: German spielen "play" gives ge-spiel-t "played", and Indonesian besar "big" gives ke-besar-an "greatness". Reduplication repeats the root: Indonesian buku "book" gives buku-buku "books".

The most striking method belongs to the Semitic languages, including Arabic and Hebrew. There, a word's root is not a string of letters in order but a set of three consonants carrying a core meaning, and the vowels belong to separate patterns that are poured over the skeleton. The root k-t-b is about writing; put it into one pattern and you get kataba "he wrote", into another kitāb "book", into another maktaba "library". The same patterns work on other roots, so madrasa "school" and maktaba "library" share a place-of pattern, built on d-r-s "study" and k-t-b "write".

Inflection and derivation: changing the form or the job

Affixes come in two kinds, and the difference runs through the whole field. Derivation makes a new word: happy to happiness changes an adjective to a noun and would get its own dictionary entry; teach to teacher names a new kind of thing. Inflection gives a form of the same word that grammar demands: dog to dogs, walk to walked. Inflection is usually regular, doesn't change the word class, and sits on the outside. In English the order is nearly always root, then derivational pieces, then inflection: nation-al-iz-ation-s, never the other way round.

Words also have structure, not just a sequence. Unlockable is ambiguous. If un- attaches to lock first, you get unlock, and then -able makes it "able to be unlocked" (a door you can open). If -able attaches to lock first, you get "lockable", and un- reverses it: "not able to be locked" (a door that will not lock). Same letters, two trees, two meanings.

Allomorphs and irregulars: one meaning, several shapes

A morpheme can take different shapes in different places; those shapes are its allomorphs. English plural -s is pronounced [s] in cats, [z] in dogs and [ɪz] in buses, chosen by the last sound of the word, as the plural tool in Phonetics and Phonology (36/21) shows. The past tense does the same: walked [t], jogged [d], wanted [ɪd]. Children apply these to words they have never heard. In Jean Berko's 1958 experiment they were shown an invented creature, "a wug", and then two of them, and said "wugz".

Then there are the exceptions: sang, geese, went. Irregulars are mostly fossils. Old English had a large class of verbs that changed their vowel to mark the past (sing, sang, sung), and over centuries most were regularised. A famous 2007 study by Erez Lieberman and colleagues followed 177 Old English irregular verbs: 145 were still irregular in Middle English, and 98 are irregular today. The striking result is which ones survive: the regularisation rate falls with the square root of how often a verb is used. A verb a hundred times as common takes about ten times as long to lose its irregular form. Frequent verbs such as be, have and go are the most irregular words in English precisely because everyone hears them so often that each form is memorised.

How the mind handles all this is a live debate. One camp, with Steven Pinker and Alan Prince, argues for words and rules: regulars come from a rule, irregulars are stored in memory. The other, going back to David Rumelhart and James McClelland's 1986 network model, holds that a single pattern-learning system handles both. Both sides agree on the data; they disagree on the machinery, and the language models of today (36/30) are a continuation of that argument.

Agglutination: building Turkish by hand

In an agglutinative language, such as Turkish, Finnish, Swahili, Quechua or Japanese, each affix carries one meaning and the pieces line up in a fixed order like train carriages. That makes the system easy to compute, so you can build the forms yourself. Turkish has one more feature: vowel harmony. The vowel in each suffix copies features from the last vowel before it, front or back and rounded or not, so that -ler becomes -lar after back vowels (okul-lar "schools") and -ler after front ones (ev-ler "houses"). Harmony is a sound rule (36/21) reaching into word-building.

Pick a noun, a number, a possessor and a case. The page assembles the word with the harmony and consonant rules. A single noun stem here gives 2 × 6 × 5 = 60 forms; with the seven stems that is 420 words, all from a handful of pieces.

Four ways to pack meaning, and why they blur

Nineteenth-century scholars sorted languages into types, and the four labels survive. Isolating (or analytic) languages, such as Mandarin and Vietnamese, use mostly one morpheme per word and leave grammar to word order and little function words: tā mǎi le sān běn shū, "he bought three books", is six words and six morphemes. Agglutinative languages stack single-meaning affixes, as above. Fusional languages pack several meanings into one inseparable ending: in Latin amō, the single -ō means "I", "now", "is a statement" and "active" all at once; you cannot cut it into four. And polysynthetic languages build whole sentences into one word. Yup'ik of Alaska can say tuntussuqatarniksaitengqiggtuq, "he had not yet said again that he was going to hunt reindeer". Nahuatl in Mexico, Chukchi in Siberia and Tiwi in northern Australia do something similar.

Linguists use these as tendencies, not boxes. Joseph Greenberg proposed in 1960 to count morphemes per word in a sample text (an "index of synthesis", with under 2 called analytic, 2 to 3 synthetic and above 3 polysynthetic, as it is usually reported). Critics point out that the labels bundle several separate dimensions, that most languages mix types (English is usually filed under fusional but is quite analytic), and that the 19th-century scheme came with a bias: some scholars ranked agglutinative or inflecting languages as more "advanced". That ranking is discredited; every language builds all the meaning its speakers need. WALS now measures the dimensions separately: how much the pieces fuse, how many meanings an ending carries, and how many places a piece can occur.

What a graduate just sees

• A word is not the unit of meaning; the morpheme is, and a word can be one or fifteen of them.
• Derivation makes new words; inflection makes the form grammar asks for, usually outside the derivation.
• Structure matters: unlockable has two trees, and so two meanings.
• One morpheme can have several shapes (allomorphs), chosen by sounds nearby.
• Irregular words survive by being common: usage frequency protects them.
• Languages can build by prefix, suffix, infix, circumfix, repetition or root-and-pattern; none is more advanced than another.
• "Isolating, agglutinative, fusional, polysynthetic" describe tendencies and dimensions, not boxes.

Where it shows up next

• Syntax (36/23): in a language with rich endings, word order can be freer, because the endings mark who did what.
• Languages of the World (36/29): typology across the globe; WALS features on fusion and exponence.
• Language Acquisition (36/27): children's over-regularisations ("goed", "foots") show them learning the rule.
• Computational Linguistics (36/30): stemmers, tokenisers and language models have to decide where words break, and agglutinative languages like Finnish and Turkish make that hard.
• In the world: spelling checkers, search engines that match "run" and "running", dictionaries, and machine translation into languages with many more word forms than English.

If you want to go deeper

• 📘 Textbook. Martin Haspelmath and Andrea Sims, Understanding Morphology (2nd edition, Routledge), which draws its examples from languages worldwide.
• 📘 Textbook. Mark Aronoff and Kirsten Fudeman, What Is Morphology? (Wiley-Blackwell, several editions), a shorter first course with exercises.
• 📘 Gentler. Steven Pinker, Words and Rules (1999), on the regular and irregular debate, written for general readers.
• 🌐 Free text. Essentials of Linguistics, 2nd edition (McMaster University), free online, with a morphology chapter: ecampusontario.pressbooks.pub/essentialsoflinguistics2.
• 🌐 Free course. MIT OpenCourseWare 24.900 Introduction to Linguistics (Spring 2022), which covers words and their structure.