By Michael McGettrickUpdated 27 September 2026
French Word-Building: Decode Words You Were Never Taught
Reading French at speed does not mean knowing every word - it means recognising the handful of patterns that build thousands of words out of a much smaller set of roots. This page covers four such patterns, all classed as reading-only on the AQA GCSE French specification: you need to recognise and understand them in a text, not necessarily produce a brand-new one from scratch. None of them needs an exercise book of vocabulary; each needs one rule.
Quick check
Three quick questions on what you have just read. The full practice is further down.
Fill in the blank
0/3Build the ordinal number from the cardinal in brackets. Watch the two spelling changes.
quatre -> (fourth)
cinq -> (fifth) (adds a u before -ième)
neuf -> (ninth) (f changes to v)
This matters more than it sounds, because exam reading are built to include words candidates have not explicitly been taught, on the assumption that a well-prepared candidate can decode them from a taught root. A student who has never met but knows (to believe) and the negating in- prefix can still work out "unbelievable" in the middle of a text under time pressure. A student who has only ever memorised whole words, with no sense of how French builds them, has to guess blind. The four patterns below are the ones most likely to pay off that way.
Ordinal numbers: add -ième to the cardinal
Most French ordinal numbers (first, second, third...) are built by taking the number and adding -ième:
- (four) -> (fourth)
- six (six) -> (sixth)
- (ten) -> dixième (tenth)
- (twenty) -> vingtième (twentieth)
Two cardinals need a small spelling tweak before the ending will attach cleanly:
- (five) -> (fifth) - a u is inserted to keep the hard "k" sound
- (nine) -> neuvième (ninth) - the final f becomes a v
Once you have the rule, you can read any ordinal in the language without ever having met it before: onzième (eleventh), quinzième (fifteenth), trentième (thirtieth) all fall out the same way.
premier, première: the one irregular ordinal
The ordinal for (one) does not follow the -ième pattern at all. Instead French uses (masculine) and (feminine) - an old, irregular pair, the way English "first" bears no to "one" while "fourth" is transparently built on "four":
- (the first day)
- (the first time)
Two details make stand out from the other ordinals. First, it agrees for gender - / (the only other ordinal that does is second/, a more formal alternative to ) - while every regular -ième ordinal stays the same for masculine and feminine and only adds -s for the plural ( , , both ). Second, the regular pattern for "one" is not entirely lost - it resurfaces inside compound numbers, where --unième is completely regular: --unième (twenty-first), --unième (thirty-first). Only the standalone ordinal for one is irregular; the compound versions are not.
The prefix in-/im-: flipping the meaning
Add in- or im- to the front of an adjective and you flip it to its opposite - exactly the job "un-" or "im-" does in English, and the spelling rule is identical too. Im- appears before a word starting with b, m or p; in- appears everywhere else:
| Base adjective | Opposite | Meaning |
|---|---|---|
| possible | impossible | possible / impossible |
| patient | patient / | |
| mobile | mobile / motionless | |
| useful / useless | ||
| capable | capable / | |
| known / unknown |
impossible à . (This problem is impossible to solve.) . (An unknown man arrived.) The same family has two further disguises worth recognising when you meet them: - before a word starting with l (lisible / illisible, readable / illegible) and ir- before r ( / irréel, real / unreal). All four spellings - in-, im-, -, ir- - are the same prefix, just absorbed into the sound that follows it.
-able / -eable: "can be done"
Strip -able from a French adjective and a verb stem is usually sitting underneath, giving a meaning of "able to be verb-ed" or "able to verb":
- (to wash) -> lavable (washable)
- (to eat) -> mangeable (edible)
- (to do) -> faisable (doable, feasible)
- (to like) -> (likeable, kind)
- (to believe) -> (believable), and with the negating prefix above, (unbelievable, incredible)
mangeable. (This dish isn't very edible.) Notice the extra e in mangeable: French inserts it whenever the verb stem ends in a "soft" g, purely to protect the pronunciation (a soft c gets a cedilla instead: remplaçable, replaceable). Without the e, "mangable" would harden the g into a completely different sound, so the spelling -eable appears specifically to stop that happening - it is the same trick as English "manageable" versus "managable".
Agent nouns via -eur / -ateur
Add -eur (or, for a smaller set of verbs, -ateur) to a verb stem and you get the noun for the person who does it - the same job "-er" or "-or" does in English:
- (to sing) -> (singer)
- (to play) -> (player)
- (to dance) -> (dancer)
- (to sell) -> (salesperson)
- (to visit) -> (visitor)
- (to
) -> organisateur () - (to direct, to make) -> (film director)
The shorter -eur is the default, attaching straight onto the verb stem; the longer -ateur usually turns up on verbs that also have a noun in -ation, such as (organisation), (réalisation) and (). This pattern is Higher-tier on the AQA specification, and it is worth reading alongside the feminine person nouns page, which covers what happens to these same nouns when the person is a woman - , danseuse, but organisatrice for the -ateur set.
More agent nouns worth recognising
Once the -eur/-ateur pattern clicks, a long tail of everyday nouns stops looking like separate vocabulary and starts looking like the same trick repeated:
- (to swim) -> nageur (swimmer)
- (to buy) -> (buyer)
- (to travel) -> (traveller)
- (to present) -> présentateur (
, TV host) - , from the same Latinate family as -ateur, though built on a Latin root rather than a modern French verb - a reminder that the pattern is old, not a
Reading a news article or a set of instructions, you will meet far more of these than any vocabulary list could pre-teach, which is exactly why the pattern is worth more than the individual words.
GCSE spec note
The ordinal and prefix patterns above are Foundation and Higher tier on the AQA GCSE French specification; the -eur/-ateur agent-noun pattern is Higher tier only. All four are classed as reading, not production - the exam wants you to decode them in a text, not necessarily spell a brand-new one correctly from memory.
Worked examples across all four patterns
- , impossible. (It's the fifth time I've tried, but it's still impossible.) - an ordinal and the in-/im- prefix in one sentence.
- , film supportable. (This book is unbelievable, but the film isn't very bearable.) - the in- prefix stacked onto an -able adjective, and a second -able adjective alongside it.
- film a . (This film's director has won several prizes.) - an -ateur agent noun in a natural sentence.
- , mangeable. (It's our first visit here, and the dish really isn't edible.) - the irregular ordinal
/next to an -able adjective, said about a bad meal.
What to do this week
- Say the ordinal
out loud -,,, dixième - until the -ième ending feels automatic, then separately drill/as the one exception. - Whenever you meet an unfamiliar adjective starting in-, im-, il- or ir-, strip the prefix first and check whether the word underneath is one you already know.
- Collect five -able adjectives from a reading
this week and check each one against its verb:,,and their -able forms are a good starting set. - If you are working towards Higher tier, add organisateur,
and présentateur to your reading vocabulary alongside the more familiar -eur nouns likeand.
Common mistakes English speakers make
Writing "unième" for "first". The regular ordinal pattern skips straight past ; the word you want is or , and unième only exists glued onto another number, as in --unième.
Guessing im- or in- at random. The choice is not free - im- only appears before b, m or p. A word like never becomes "imutile" because u is not one of the three trigger letters.
Dropping the extra e in mangeable. The e is doing real phonetic work, not decoration - without it, the g would harden into a different sound entirely.
Assuming every -eur noun takes the same ending. This page is about spotting the pattern when reading; producing the correct feminine form (-euse or -rice) is a separate skill covered on its own page, linked above.
See also
- French cognate patterns - the English-to-French ending swaps that decode borrowed vocabulary, the sister skill to this page's home-grown French patterns.
- French feminine person nouns - what happens to -eur and -ateur agent nouns when the person referred to is a woman.
- French adjective agreement - how
/and the -able adjectives behave once they start agreeing with a noun.