B2 (Upper Intermediate)Lesson 4: Word Formation
A couple of dozen prefixes turn words you already know into several more: des- undoes, re- repeats, in-/im-/i-/ir- negates, super- exaggerates, pré- and pós- place things in time. This point covers what each family means, how in- reshapes itself to fit the word behind it, and the hyphen rules that decide between micro-ondas and autoescola.
des- is the workhorse — it undoes, switches off and negates: *fazer → desfazer* (to undo), *ligar → desligar* (to switch off), *conhecido → desconhecido* (unknown).
in- reshapes itself to fit: im- before p and b (impossível — impossible), i- before l (ilegal — illegal), ir- before r (irreal — unreal), in- everywhere else (infeliz — unhappy).
re- means again or back: *ver → rever* (to review), *começar → recomeçar* (to start over).
The position prefixes place things in space and time: sub- under (subsolo — basement), sobre- over (sobrecarga — overload), ante- before (anteontem — the day before yesterday), pré-/pós- (pós-graduação — postgraduate study).
super-, hiper-, mega-, ultra-, extra- are the intensity family and Brazilians stick them on anything: supercansado (super tired), megafestival (huge festival).
The hyphen shows up only when the letters collide (micro-ondas — microwave) or the root starts with h (super-homem — superman); otherwise write it solid: autoescola (driving school).
Stressed pré-, pós-, pró- always keep hyphen and accent (pré-pago — prepaid); the unstressed ones never do (proativo — proactive).
prefix + word you already know → des- (undo) · re- (again) · in-/im-/i-/ir- (not) · super- (very) — hyphen only when the letters collide or the root starts with h
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At B2 your grammar has overtaken your vocabulary, and a Brazilian newspaper still hands you twenty unknown words a page. Prefixes are the cheapest repair available: two dozen small pieces, each one multiplying every word you already own. They work in the reading direction too — meet desabastecimento (shortage) or reeleição (re-election) for the first time and you can take them apart instead of reaching for the dictionary. And they are alive right now: Brazilians coin superatrasado (super late) and pós-pandemia (post-pandemic) on the spot, and expect you to keep up.
des- is the living, working prefix of Brazilian Portuguese. It attaches to verbs, nouns and adjectives, and it undoes, switches off or negates whatever it finds:
| Base word | With des- | Meaning |
|---|---|---|
| fazer (to do) | desfazer | to undo |
| ligar (to switch on) | desligar | to switch off, to hang up |
| arrumar (to tidy) | desarrumar | to mess up |
| congelar (to freeze) | descongelar | to defrost |
| aparecer (to appear) | desaparecer | to disappear |
| marcar (to schedule) | desmarcar | to cancel a plan |
| Portuguese | Meaning |
|---|---|
| Desliga a luz antes de sair, por favor. | Turn off the light before you leave, please. |
| Precisamos refazer o relatório inteiro. | We need to redo the whole report. |
| O restaurante fica no subsolo do shopping. | The restaurant is in the basement of the mall. |
| Ele foi irresponsável ao dirigir sem carteira. | He was irresponsible, driving without a licence. |
| Cheguei em casa supercansada depois do trabalho. | I got home super tired after work. |
| Ela terminou a pós-graduação em dezembro. | She finished her postgraduate degree in December. |
| Esse remédio é um anti-inflamatório forte. | That medicine is a strong anti-inflammatory. |
| Aquecemos o arroz no micro-ondas. | We heated the rice up in the microwave. |
Using des- to translate every English "un-". With adjectives, English "un-" is usually the in- family: ❌ desfeliz → ✅ infeliz (unhappy); ❌ descapaz → ✅ incapaz (incapable). Des- is right on participles and verbs: desconhecido (unknown), despreparado (unprepared), desligar (to switch off).
*Confusing ante- with anti-.* Ante- is time, anti- is opposition: ✅ anteontem (the day before yesterday) but ✅ antibiótico (antibiotic). ❌ antiontem is a very common learner slip.
Writing the intensity prefixes as separate words. They are prefixes, so they join: ❌ super cansado → ✅ supercansado (super tired); ❌ mega festa → ✅ megafesta (huge party). You will see them split all over social media; keep them joined in anything you sign.
Hyphenating by default. The hyphen is the exception: ❌ super-mercado, ❌ anti-aéreo → ✅ supermercado (supermarket), ✅ antiaéreo (anti-aircraft). The 1990 orthographic agreement also removed old ones you will still meet on old signs: ❌ anti-social → ✅ antissocial, ❌ auto-escola → ✅ autoescola.
*Dropping the accent on pré- and pós-.* Stressed, they keep accent and hyphen: ❌ pos graduação → ✅ pós-graduação (postgraduate study). Their unstressed cousins do the opposite and take neither: ✅ proativo (proactive), ✅ preexistente (pre-existing).
Reading the prefix instead of the word. Reparar is not "to re-pair": Você reparou no cabelo dela? (Did you notice her hair?) And desistir is not "to un-exist": Ele desistiu do curso. (He gave up on the course.)
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