Schwa tends to be elided when it occurs before the sonorants /r,l,n/, followed by a weak vowel. Schwa-elision is more common in frequent words than in infrequent words. In very common words like general and different schwa is readily elided even in careful styles: /ˈd͡ʒɛnrəl, ˈdɪfrənt/. In fact, the word every is normally /ˈɛvri/ in all styles.
In addition to this, the frequency of elision depends on the phonetic context. It is most common between an obstruent or nasal and /r/, as in separate, history, elaborate, nursery, century, camera, memory, scenery, though after /k,g/ it is less common, as in bakery, mockery, vagary /ˈveɪgəri/.
Before /l/ and /n/, as in family, finally, privilege, passionate, arsenal, schwa-elision may create a syllabic consonant, i.e. /ˈfæml̩i, ˈfaɪnl̩i, ˈprɪvl̩əd͡ʒ, ˈpæʃn̩ət, ˈɑrsn̩əl/, which in more rapid styles may lose its syllabic status, giving rise to disyllabic /ˈfæmli, ˈfaɪnli, ˈprɪvləd͡ʒ, ˈpæʃnət, ˈɑrsnəl/.
In words like artery, cidery, rotary, uterus, watery, malodorous schwa is normally retained: apparently, previous application of flapping blocks schwa-elision. In this connection it is worth noting that elision does not normally occur after /l,r/ either, so that /ə/ is retained in salary, quarreling, colony, mariner.
In very rapid speech schwa may also be elided before a stressed vowel, as in police, believe, marine, collapse, sonata, solarium. Here again, we can distinguish between cases where the loss of schwa is compensated for the creation of a syllabic consonant, as in (disyllabic) /pl̩iːs, bl̩iːv, mr̩iːn/, and the more extreme monosyllabic forms pliːs, bliːv, mriːn/, where no such compensation takes place.
A different type of schwa-elision may occasionally be heard in non-standard speech when /r/ occurs between two schwas. In words like different, dangerous, ignorant, the second rather than the first schwa may be elided, yielding /ˈdɪfərnt, ˈdeɪnd͡ʒərs, ˈɪgnərnt/. Because of the low prestige associated with these pronunciations, hypercorrections may arise like */ˈmɑːdrən/ for modern, i.e. /ˈmɑːdərn/ (Bailey 1985:125).
Schwa-elision is particularly common in frequent words like different, history, camera, family.
Avoid schwa-elision before non-sonorants: Many Dutch speakers are inclined to apply elision in words like difficult, physical, relative, syllable, political, development, pronouncing them */ˈdɪfkʌlt, ˈfɪskəl, ˈrɛltɪf, ˈsɪlbəl, pəˈlɪtkəl, dɪˈvɛlpmənt/. A similar undesirable elision is commonly heard in final unaccented syllables, as in crisis, packet, which may be pronounced */ˈkraɪss̩, ˈpækt/.
Here are some examples of words where schwa-elision is common: reference, prisoner, personal, opera, especially.