Decoding exercises: "io"

The sequence "io" normally is part of two syllables (as in "sociology") or the "i" modifies the sound of the previous letter as in "action". This page sets out some words teachers can use to help their students become more aware of how they can sound out more correctly the different sounds corresponding to words containing "io".

Modified "c", "s", "t" + "io"

 * See also: Decoding exercises: "sion", Decoding exercises: "tion"

The letters "c", "s" and "t" often change their sound when followed by an "i".


 * "cio" as /ʃə/: suspicion
 * "cio" as /ʃə/ or /ʒə/: coercion
 * "sio"
 * as /ʒə/: conclusion, confusion, decision, division, explosion, occasion, occasional, precision, provision, television, vision, visionary
 * as /ʃə/: compulsion, extension, pension, propulsion, revulsion, tension, torsion


 * "ssio" as /ʃə/: admission, aggression, compassion, compassionate, confession, depression, discussion, mission, missionary, profession
 * "tio"
 * as /ʃə/: action, addition, additional, condition, education, function, functional, information, nation, organization, position, relation, situation, tradition, traditional
 * as /ʃə/ or /ʃ/: national
 * as /tʃə/: question, suggestion
 * as /ʃə/ or /tʃə/: attention, intention, mention
 * as /ʒə/: equation
 * as /ʃiːəʊ/: ratio

Unmodified "c", "s", "t" + "io"

 * "cio" as /siːəʊ/: nuncio, sociocultural
 * "cio" as /siːɒ/: sociology
 * "cio" as /siːə/: sociological
 * "sio" as /ziːəʊ/: physiotherapy
 * "sio" as /ziːɒ/: anaesthesiology, anesthesiology, physiology
 * "tio" as /tiːə/: bastion

Two syllables

 * /aɪɒ/: biology
 * /aɪɒ, aɪɔː/: priority
 * /aɪəʊ/: Ohio
 * /aɪə/: Iowa, lion, prior, violence
 * /iːəʊ/: cardio, cardiovascular, Ethiopia, studio
 * /iːɒ/: cardiology
 * /iːə/: champion, criterion, interior, period, radio, senior, union

One syllable

 * /jə/: behavior, behaviour, billion, onion, opinion
 * /ə/: region, religion, fashion

Variant pronunciations

 * /ʃiːɒ, siːɒ/: glaciology

"ious"

 * "ious" as /iːəs/: curious, obvious, previous, serious, various
 * "ious" as /əs/: anxious, religious
 * "cious" as /ʃəs/: atrocious, audacious, auspicious, conscious, delicious, malicious, precious, suspicious