-cious, -tious, -cial and -tial

The 'shus' sound: -cious or -tious?

Adjectives such as delicious, ambitious and suspicious end in a 'shus' sound. The choice between -cious and -tious usually comes from a related word:

• If the root ends in -ce, use -cious: grace, gracious; space, spacious; malice, malicious; vice, vicious.
• If there's a related noun ending in -tion, use -tious: ambition, ambitious; caution, cautious; infection, infectious; nutrition, nutritious.

• spaciousFrom space.
• cautiousFrom caution.

Anxious is the well-known exception: it ends in -xious, linked to anxiety. It's worth a mention so children don't try to force it into one of the two groups.

The 'shul' sound: -cial or -tial?

For words such as special and essential, the National Curriculum guideline is that -cial usually follows a vowel and -tial usually follows a consonant.

• official, special, artificialAfter a vowel: -cial.
• partial, confidential, essentialAfter a consonant: -tial.

The guideline has some common exceptions that are worth learning by sight: initial, financial, commercial and provincial. Related words help here too: finance ends in -ce, which matches financial; commerce matches commercial.

Use the word family

For both endings, the most powerful strategy is to look for a related word. Most of these adjectives have a noun or verb cousin whose spelling gives the game away: office, official; confidence, confidential; suspicion, suspicious. Encourage children to say “what does this come from?” before they write.

In the SATs

These endings appear in the National Curriculum's Year 5 and 6 spelling appendix, and words such as delicious, suspicious, special and essential are exactly the kind of vocabulary the SATs spelling paper uses. Each of the 20 words is read alone, then in a sentence, then alone again, so children have time to think about the root before they write.

Common mistakes

• delishusPhonetic spelling. It's delicious.
• ambiciousRelated to ambition, so ambitious.
• essencialAfter a consonant: essential.

• Writing the sound phonetically: -shus, -shul.
• Swapping c and t, especially in suspicious and ambitious.
• Forgetting the i: specal, delicous.
• Applying the vowel/consonant guideline to the exceptions.

Teaching ideas

Family trees

Give pupils the adjective and ask them to find its relative: vicious and vice, nutritious and nutrition. Displaying the pairs side by side with the matching letters highlighted makes the link visible.

Vowel or consonant?

For -cial and -tial, give pupils the start of each word (offi___, par___) and ask them to look at the letter before the gap. Then reveal the exceptions as a challenge round.

Describe it

Show pictures (a huge kitchen, a cake, a nervous cat) and ask pupils to describe each using words from the lists: spacious, delicious, anxious. Using the words in context helps them stick.

Dictation

Use the sentences on the sheets for short dictations, three or four words at a time, mixing c and t words so children have to choose each time.

Try it: five quick questions

SATs-style questions to use as a starter or a quick check. Tap to see each answer.

1. Which is correct? gracious / gratious

   Show answer

   gracious: from grace.

2. Which is correct? infecious / infectious

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   infectious: from infection.

3. Fill the gap: offi___ (approved by people in charge)

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   official: -cial after a vowel.

4. Fill the gap: confiden___ (secret)

   Show answer

   confidential: -tial after a consonant.

5. Which word breaks the vowel/consonant rule? special, partial, initial

   Show answer

   initial: -tial after a vowel.