CDS English · Vocabulary
Spelling: double letters, silent letters and vowel traps
Four spellings of one word, three of them wrong. Check the double letters, the silent Greek letters and the vowels in the middle, in that order.
Why this matters
Spelling items came as a block in the 2019 (II) and 2020 papers. The words are ones every officer writes: commissioner, strategy, accommodate. The wrong options fail in a few fixed ways, so a three-point check catches almost all of them.
Concept 1 of 3: Count the double letters
Most spelling items turn on a double consonant: two of the same consonant side by side (cc, mm, ss). The wrong options drop one of the pair, or double the wrong letter. So count the doubles first. It is the fastest check and it removes most options.
Definition
The method:
- Say the word in syllables: em-bar-rass-ment.
- At each syllable, ask whether the consonant is doubled.
- Strike every option with too few or too many doubles.
- Between the survivors, check the vowels (see the third concept on this page).
Words tested, with their doubles:
- 2019 (II): accommodate (cc and mm), recommend (one c, mm), aggressive (gg and ss), assassination (ss and ss), embarrassment (rr and ss).
- 2020 (I): commissioner (mm and ss), supplementary (pp, ending -ary), vacuum (uu, a double vowel).
- 2020 (II): snobbery (bb), etiquette (tt, ending -ette).
Worked example
Choose the correctly spelt word. (a) Comittee (b) Committe (c) Committee (d) Commitee
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2019 · CDS (II) 2019 — English · Q7Moderate
Example 1 · Vocabulary · Spelling
Directions: pick the correctly-spelt word
Choose the correctly spelt word.
Recommend has one c
Accommodate doubles both c and m, so students double both in recommend too. Recommend = re + commend: one c, two m.
Harass is not like its neighbours
Harass has one r and two s. Students double the r by analogy with words like arrest and arrange. Learn it as an exception.
Doubles can be vowels
Vacuum and continuum have a double u. Options such as 'vacum' or 'vacuem' fail because they drop or change the second u.
Concept 2 of 3: Greek spellings and silent letters (ps-, pn-, ph-)
Many medical and scientific words come from Greek. They keep Greek letter groups that English does not say: a silent letter p in ps- and pn-, and ph for the f sound. If a word names a science, a disease or a study, expect these letter groups.
Definition
Letter groups to expect:
- ps- at the start, p silent: psephology, pseudonym, psychology.
- pn- at the start, p silent: pneumonia (pneuma = breath, lung).
- ph for the f sound: nephrology (nephros = kidney), diphtheria.
- eu for the 'yoo' sound: pseudonym, pneumonia, neurosis.
- -ology = the study of; -osis = a condition.
| Word | Meaning | Spelling point | Sitting |
|---|---|---|---|
| Psephology | The study of elections and voting | Silent p; ph for f | 2020 (I) |
| Nephrology | The study of the kidneys | ph for f; no u after Ne | 2020 (I) |
| Pseudonym | A false name used by a writer | Silent p; -eu-; -nym = name | 2020 (I) |
| Pneumonia | An infection of the lungs | Silent p; -eu- | 2020 (I) |
| Diphtheria | A serious throat infection | ph and then th | 2020 (II) |
| Neurosis | A mental disorder marked by anxiety | -eu-; ending -osis | 2020 (II) |
| Twelfth | Coming after the eleventh | Twelve turns its v into f: twel-f-th | 2020 (II) |
Silent letters do not show in speech, so spell these from the meaning: pneuma (lung), pseudo (false), nephros (kidney).
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2020 · CDS (I) 2020 — English · Q98Moderate
Example 2 · Vocabulary · Spelling
Directions: choose the correctly spelt alternative
Which one of the following alternatives has the correct spelling?
Dropping the silent letter
Options like 'sephology' or 'sychology' spell the word as it sounds. The silent p is part of the word. If the word is medical or scientific, check the start for ps- or pn-.
Ph followed by th
Diphtheria has ph and then th. Students write 'diptheria' because they say it that way. Spell it as diph-the-ria.
Twelfth keeps its f
Twelve becomes twelfth, not 'twelth'. The f is weak in speech but must be written.
Concept 3 of 3: Vowel traps and word endings
Once the consonants are right, the wrong options change a vowel in the middle (stretegy) or the ending (magnificant). The fix is to go back to the base word: argue gives argument, mountain gives mountainous, strata gives strategy.
Definition
Rules that help:
- Drop the silent e before -ment in a few words: argue becomes argument (not arguement).
- Keep the base word and add the ending: mountain + -ous = mountainous.
- -ent / -ient for adjectives from Latin -ens: magnificent, resilient.
- -re is the British ending in meagre, centre, theatre.
- Latin nouns end in -um: curriculum, continuum.
| Word | Spelling point | Typical wrong option | Sitting |
|---|---|---|---|
| Argument | argue drops its e before -ment | Arguement | 2019 (II) |
| Decisive | de-ci-sive: c then s | Desisive | 2019 (II) |
| Continuum | Latin -um after a double u | Continuem | 2020 (I) |
| Strategy | stra- then -tegy: a then e | Stretegy | 2020 (I) |
| Resilient | re- then -silient, ending -ient | Risilient | 2020 (I) |
| Mountainous | mountain + -ous, no extra vowel | Mountaineous | 2020 (II) |
| Curriculum | rr, then Latin -um | Curriculam | 2020 (II) |
| Magnificent | ending -cent | Magnificant | 2020 (II) |
| Felicitation | fe-li-ci-ta-tion: e, then i, i | Falicitation | 2020 (II) |
| Meagre | British -re ending | Megare | 2020 (II) |
Build the word from its base, then check the ending against a word you trust.
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2019 · CDS (II) 2019 — English · Q3Easy
Example 3 · Vocabulary · Spelling
Directions: pick the correctly-spelt word
Choose the correctly spelt word.
Keeping the e of the base word
Most words keep their e before -ment (judgement in British use, movement), so students write 'arguement'. Argument is the exception to learn.
Adding a vowel that is not there
Mountainous is mountain + -ous. 'Mountaineous' borrows the e of mountaineer. Build the word from its base and add nothing.
-ent or -ant
Magnificent, resilient and decisive are checked by the middle and the ending. When unsure, think of a related word: magnificence, resilience.
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Greek spellings and silent letters (ps-, pn-, ph-)7 rows
| Word | Meaning | Spelling point | Sitting |
|---|---|---|---|
| Psephology | The study of elections and voting | Silent p; ph for f | 2020 (I) |
| Nephrology | The study of the kidneys | ph for f; no u after Ne | 2020 (I) |
| Pseudonym | A false name used by a writer | Silent p; -eu-; -nym = name | 2020 (I) |
| Pneumonia | An infection of the lungs | Silent p; -eu- | 2020 (I) |
| Diphtheria | A serious throat infection | ph and then th | 2020 (II) |
| Neurosis | A mental disorder marked by anxiety | -eu-; ending -osis | 2020 (II) |
| Twelfth | Coming after the eleventh | Twelve turns its v into f: twel-f-th | 2020 (II) |
Silent letters do not show in speech, so spell these from the meaning: pneuma (lung), pseudo (false), nephros (kidney).
Vowel traps and word endings10 rows
| Word | Spelling point | Typical wrong option | Sitting |
|---|---|---|---|
| Argument | argue drops its e before -ment | Arguement | 2019 (II) |
| Decisive | de-ci-sive: c then s | Desisive | 2019 (II) |
| Continuum | Latin -um after a double u | Continuem | 2020 (I) |
| Strategy | stra- then -tegy: a then e | Stretegy | 2020 (I) |
| Resilient | re- then -silient, ending -ient | Risilient | 2020 (I) |
| Mountainous | mountain + -ous, no extra vowel | Mountaineous | 2020 (II) |
| Curriculum | rr, then Latin -um | Curriculam | 2020 (II) |
| Magnificent | ending -cent | Magnificant | 2020 (II) |
| Felicitation | fe-li-ci-ta-tion: e, then i, i | Falicitation | 2020 (II) |
| Meagre | British -re ending | Megare | 2020 (II) |
Build the word from its base, then check the ending against a word you trust.
Watch out for (9)
- Recommend has one c→ Count the double letters
- Harass is not like its neighbours→ Count the double letters
- Doubles can be vowels→ Count the double letters
- Dropping the silent letter→ Greek spellings and silent letters (ps-, pn-, ph-)
- Ph followed by th→ Greek spellings and silent letters (ps-, pn-, ph-)
- Twelfth keeps its f→ Greek spellings and silent letters (ps-, pn-, ph-)
- Keeping the e of the base word→ Vowel traps and word endings
- Adding a vowel that is not there→ Vowel traps and word endings
- -ent or -ant→ Vowel traps and word endings
Test yourself on Vocabulary
20 past CDS questions from this chapter, timed at 20 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.