MockoWhen you meet an unfamiliar word in a TCF reading or vocabulary item, the prefix is often the fastest clue to its meaning. French shares most of its prefixes with Latin and Greek, which means that knowing about 20 common prefixes lets you decode hundreds of words you have never seen before. This lesson focuses on the prefixes that appear most often in TCF-level texts and shows how to use them reliably in multiple-choice items.
What you’ll learn
- Recognise the most common French prefixes and their core meanings
- Use prefix analysis to infer the meaning of unfamiliar words in context
- Distinguish prefixes that look similar but carry different meanings
- Apply prefix knowledge to eliminate wrong options in TCF QRU vocabulary items
Why prefixes matter in the TCF
TCF vocabulary items at B1 level regularly include words that a test-taker at that level might not have learned directly: "inadapté," "prédéfini," "surestimer," "déséquilibre." If you know the base word and the prefix, you can often work out the meaning without having memorised the compound form.
The prefix alone is not always enough, especially when several prefixes look similar (in-, im-, ir-, il- all appear). Context always has the final say. But prefix knowledge reduces four options to one or two, and context closes the gap.
Two-step approach
- Step 1: Identify the prefix and its meaning (negation? reversal? before? excessive?).
- Step 2: Combine that meaning with the base word and check against the sentence context.
Negation prefixes: in-, im-, ir-, il-, dés-, non-
These prefixes all express negation or the absence of a quality. The choice of form depends on the first letter of the base word. They are among the most productive prefixes in French and appear in very common words.
- "in-" before most consonants: inutile (useless), incertain (uncertain), indirect (indirect), invisible
- "im-" before b, m, p: impossible, impartial, imbattable, immobile
- "ir-" before r: irresponsable (irresponsible), irréel (unreal), irrégulier
- "il-" before l: illégal (illegal), illisible (illegible), illogique
- "dés-" for reversal or negation of a process: désaccord (disagreement), désavantage, désorganiser, désactiver
- "non-" for neutral negation, often hyphenated: non-fumeur (non-smoker), non-remboursable, non-stop
Le formulaire doit être rempli de façon ________ pour être accepté. (A) illisible (B) lisible (C) illégale (D) légale
A form must be filled in a way that allows it to be accepted. That means it must be readable, not unreadable. "Lisible" (readable) fits. "Illisible" (illegible) would cause rejection. The prefix "il-" marks negation. Context confirms the positive form is needed here.
"In-" can also mean "into" or "inward"
- Not every word starting with "in" carries a negation: "information," "ingrédient," "inspection" all start with "in" but it is not a negation prefix there.
- The negation reading applies when there is a recognizable base adjective or noun: "in + capable = incapable."
- When in doubt, look for the base word. If "capab-" means capable, then "incapable" means not capable.
Reversal and repetition: dé(s)-, re-, r-
"Dé(s)-" reverses an action or undoes a state. "Re-" (or "r-" before a vowel) means doing something again or returning to a previous state. These are extremely productive prefixes and appear in everyday French.
- "dé-": défaire (to undo), décourager (to discourage), débloquer (to unblock), déménager (to move out)
- "dés-": déshabiller (to undress), désordre (disorder), décourager
- "re-": refaire (to redo), relire (to reread), revenir (to come back), renouveler (to renew)
- "r-" before vowel: rouvrir (to reopen), rallumer (to relight), racheter (to repurchase)
Suite aux travaux, la piscine rouvrira ses portes le lundi 5 septembre à partir de 9h.
Following the renovation work, the swimming pool will reopen its doors on Monday 5 September from 9 a.m. "R-" + "ouvrir" = "rouvrir" (to open again). The prefix signals that the pool was open before, closed for works, and will open again.
Après l'incident, le directeur a dû ________ toute l'organisation du projet. (A) refaire (B) défaire (C) faire (D) parfaire
"Refaire" means to redo or reorganize entirely, which fits the idea of having to restart. "Défaire" means to undo or dismantle. "Faire" is too neutral. "Parfaire" means to perfect or complete, which does not match the context of recovering from an incident.
Position and degree: pré-, post-, sur-, sous-, co-, inter-
These prefixes express spatial or temporal position, degree, or relationship. They appear frequently in formal and journalistic texts at B1 to B2 level.
- "pré-" (before): prévoir (to foresee), préalable (prior/preliminary), prédéfini (predefined)
- "post-" (after): postérieur (subsequent), post-opératoire (post-operative)
- "sur-" (over, excess): surestimer (to overestimate), surcharger (to overload), surpasser
- "sous-" (under, insufficient): sous-estimer (to underestimate), sous-développé, sous-titres (subtitles)
- "co-" (together, joint): cohabiter (to cohabit), coopérer, cofondateur (co-founder)
- "inter-" (between): interdépendant, internationale, intermédiaire (intermediary)
Les experts pensent que les autorités ont ________ les risques liés à cet événement. (A) surestimé (B) sous-estimé (C) préestimé (D) postestimé
The context needs to say whether the authorities over- or underestimated the risks. Without more surrounding context both "surestimé" and "sous-estimé" seem possible. This shows why you must read the whole passage: if the article criticises the authorities for being caught off guard, "sous-estimé" (underestimated) fits. If it criticises panic, "surestimé" (overestimated) fits. "Préestimé" and "postestimé" are not standard French.
Sur- vs sous-: check the outcome described
- If the text describes excess (too much, too heavy, too expensive): look for "sur-."
- If the text describes insufficiency (not enough, too little, neglected): look for "sous-."
- The words that follow often give the clue: "résultat insuffisant" points to "sous-estimé"; "charge trop lourde" points to "surchargé."
Other high-frequency prefixes
These prefixes appear regularly in B1-level reading and vocabulary items and are worth knowing as a group.
- "anti-" (against): anticiper (to anticipate), anticoagulant, antipollution, antivol (anti-theft)
- "auto-" (self): autonome (autonomous), autosuffisant (self-sufficient), autoformation (self-study)
- "bi-/tri-" (two/three): bilingue (bilingual), bimensuel (twice monthly), trilingue, trimestre
- "micro-/macro-": microentreprise (micro-business), macroéconomie
- "hyper-/hypo-": hyperactif (hyperactive), hypothèse, hypersensible
- "télé-" (remote, far): télétravail (remote work), télécommunication, télécharger (to download)
Depuis la pandémie, le télétravail s'est généralisé dans de nombreux secteurs professionnels.
Since the pandemic, remote working has become widespread across many professional sectors. "Télé-" (from a distance) + "travail" (work) = work done from a distance. Knowing the prefix makes the word immediately transparent.
How to practise this
Prefix knowledge grows with exposure. The most useful practice is to notice prefixes in texts you are already reading and to group new vocabulary by prefix family rather than learning words in isolation.
Prefix study habits
- When you learn a new word, strip off the prefix and write the base word next to it: "inadapté" = in + adapté (not adapted).
- Make a prefix map: draw a circle for each prefix and add words as you find them. Add new words to the right circle when you meet them.
- For TCF practice, when a vocabulary item has an unfamiliar word, try to identify the prefix before reading the options. Write out what the prefix means.
- Read one short French article per day and circle every word with a recognizable prefix. Try to define the word from the prefix alone before reading further.
Key takeaways
- Negation prefixes (in-, im-, ir-, il-, dés-, non-) all mean "not" or "without", the form depends on the first letter of the base word.
- "Dé(s)-" reverses an action; "re-" repeats it or returns to a previous state.
- "Sur-" signals excess; "sous-" signals insufficiency.
- "Pré-" means before; "post-" means after; "co-" means together.
- Prefix analysis is a first filter, not a final answer, always confirm with sentence context.
