English has a remarkable property: adding a suffix often changes not just the word's meaning, but also which syllable gets the stress and how vowels sound. Understanding these patterns will help you pronounce derived words (words formed by adding prefixes or suffixes) correctly. When stress moves, unstressed vowels often reduce to schwa /ə/.
Pattern 1: -TION/-SION Shifts Stress to the Suffix
When you add -TION or -SION to a base word, the stress shifts to that new syllable, and vowels in previously stressed syllables often change.
Pattern: Base stress + -TION/SION = stress on the suffix (sion/tion)
Examples:
- pronounce /ˈproʊnaʊns/ becomes pronunciation /ˌproʊnənsiˈeɪʃən/ (stress moves from first to third syllable)
- music /ˈmjuzɪk/ becomes musician /mjuˈzɪʃən/ (stress shifts to second syllable)
- decide /dɪˈsaɪd/ becomes decision /dɪˈsɪʒən/ (base stress stays on same syllable but vowel changes)
- examine /ɪɡˈzæmɪn/ becomes examination /ɪɡˌzæməˈneɪʃən/ (stress shifts to final syllable)
Vowel quality change: Vowels that lose stress become schwa /ə/ or are reduced. The first vowel in "pronounce" /aʊ/ becomes schwa-like in "pronunciation."
Pattern 2: -IC Shifts Stress to the Preceding Syllable
When you add the suffix -IC to a base word, stress often shifts to the syllable immediately before the IC.
Pattern: Base stress + -IC = stress on syllable before IC
Examples:
- photograph /ˈfoʊtəɡræf/ becomes photographic /ˌfoʊtəˈɡræfɪk/ (stress shifts from first to third syllable)
- economy /ɪˈkɑnəmi/ becomes economic /ˌɛkəˈnɑmɪk/ (stress on second syllable of suffix area)
- electric /ɪˈlɛktrɪk/ stays stressed on second syllable, but in electrician stress shifts further
- atom /ˈætəm/ becomes atomic /əˈtɑmɪk/ (stress moves from first to second syllable)
Vowel quality change: Unstressed syllables reduce. The first vowel in "photograph" /oʊ/ becomes schwa-like quality in some contexts.
Pattern 3: -ITY Shifts Stress to the Preceding Vowel
Adding -ITY (which means a state or condition) almost always shifts stress to the vowel immediately before the ITY ending.
Pattern: Base word + -ITY = stress on vowel before ITY
Examples:
- electric /ɪˈlɛktrɪk/ becomes electricity /ɪˌlɛkˈtrɪsəti/ (stress moves to third syllable)
- popular /ˈpɑpjələɹ/ becomes popularity /ˌpɑpjəˈlæɹəti/ (stress moves from first to second-to-last)
- stupid /ˈstupɪd/ becomes stupidity /stuˈpɪdəti/ (stress moves from first to second)
- curious /ˈkjuɹiəs/ becomes curiosity /ˌkjuɹiˈɑsəti/ (stress moves to second-to-last)
Vowel quality change: Previous stressed vowels become reduced because stress shifts. All unstressed syllables use schwa /ə/.
Pattern 4: -ICAL Keeps Stress in the Same Location as -IC
When you add -ICAL (instead of just -IC), the stress pattern is similar to -IC alone. Stress stays on the syllable before ICAL.
Pattern: Base + -ICAL = stress on the syllable before ICAL (consistent with -IC pattern)
Examples:
- economy /ɪˈkɑnəmi/ becomes economical /ˌɛkəˈnɑmɪkəl/ (stress on second-to-last syllable)
- magic /ˈmædʒɪk/ becomes magical /ˈmædʒɪkəl/ (stress stays on first syllable)
- dramatic /dɹəˈmætɪk/ becomes dramatical (archaic) or the pattern holds
- systematic /ˌsɪstəˈmætɪk/ becomes systematical with same stress location
Key insight: Adding -AL to -IC doesn't change the stress from -IC. The -AL is just an extra unstressed suffix.
Vowel quality change: The final -AL creates an unstressed syllable with schwa /əl/.
Pattern 5: -OUS Can Shift Stress (Variable Pattern)
The suffix -OUS (meaning full of or having the quality of) often shifts stress, though it's less predictable than -ITY or -TION.
Pattern: Base + -OUS = stress typically on the syllable before OUS or base stress maintained
Examples:
- mystery /ˈmɪstɛɹi/ becomes mysterious /mɪˈstɪɹiəs/ (stress moves from first to second syllable)
- danger /ˈdeɪndʒɚ/ becomes dangerous /ˈdeɪndʒɚəs/ (stress stays on first syllable but vowel in second becomes schwa)
- glory /ˈɡlɔɹi/ becomes glorious /ˈɡlɔɹiəs/ (stress typically on first)
- humor /ˈhjumɚ/ becomes humorous /ˈhjumɚəs/ (stress on first, reduced final)
Note: -OUS is always pronounced /əs/ in stressed position or /əs/ when unstressed. The OUS always reduces to /əs/.
Pattern 6: -AL Often Adds an Unstressed Syllable
The suffix -AL (meaning relating to or of the nature of) typically adds an unstressed final syllable. It rarely shifts stress from the base word.
Pattern: Base + -AL = stress stays on base word; -AL becomes /əl/ (unstressed)
Examples:
- person /ˈpɝsən/ becomes personal /ˈpɝsənəl/ (stress stays on first; -AL adds schwa-l)
- emotion /ɪˈmoʊʃən/ becomes emotional /ɪˌmoʊʃənəl/ (stress on second; -AL adds unstressed)
- tradition /trəˈdɪʃən/ becomes traditional /trəˈdɪʃənəl/ (stress on second; -AL adds unstressed)
- music /ˈmjuzɪk/ becomes musical /ˈmjuzɪkəl/ (stress on first; -AL adds unstressed)
Key insight: -AL is usually a stress-neutral suffix. It doesn't change where stress lands; it just extends the word.
Pattern 7: -IZE/-ISE Typically Keeps Base Stress
The suffix -IZE (to cause to become) or -ISE (British spelling) usually keeps stress on the base word. The suffix itself is not typically stressed.
Pattern: Base + -IZE/ISE = stress stays on base; suffix unstressed
Examples:
- memory /ˈmɛmɔɹi/ becomes memorize /ˈmɛmɚaɪz/ (stress on first syllable; -IZE is unstressed)
- terror /ˈtɛɹɚ/ becomes terrorize /ˈtɛɹɚaɪz/ (stress on first; -IZE is unstressed)
- hospital /ˈhɑspɪtəl/ becomes hospitalize /hɑˈspɪtəlaɪz/ (stress moves slightly or stays similar)
- final /ˈfaɪnəl/ becomes finalize /ˈfaɪnəlaɪz/ (stress stays on first; -IZE unstressed)
Key insight: -IZE is similar to -AL in that it usually doesn't pull stress to itself. The main difference: -IZE creates a new stressed-like syllable with the long I /aɪ/ before the Z.
Key Takeaway: Stress and Vowel Reduction
The critical principle across all these patterns is this: when a suffix is added and stress shifts, vowels in syllables that are no longer stressed reduce to schwa /ə/. This is why English sounds so different when suffixes are added. The pronunciation changes not just because of the suffix itself, but because stress placement determines vowel quality. Pay attention to which syllable is stressed when you learn a derived word, and the vowel quality will follow naturally.