Six prefixes that change meaning from the front
A prefix goes before the base word and changes its meaning without changing its class: cook is still a verb in overcook. Tap a prefix and read what it does. (El prefijo va delante y cambia el significado; la clase de palabra no cambia.)
1 · Turn the dial
Base + prefix → a new word (or no word at all)
Tap a base word, then tap a prefix to attach it. The machine builds the word and explains the change of meaning. Careful: not every prefix fits every base. (Toca la base y luego el prefijo; no todas las combinaciones existen.)
Which one does this word take?
Spelling, pairs, twins & productivity
Errors Spanish speakers make
Read the word or sentence, find the problem, then tap Fix to check. (Adivina la corrección antes de verla.)
👩🏫 For the teacher — how this page maps to the manual
- Explore is Structure 13 in two devices: the dial (the six prefixes of the manual's table with their meaning and word lists) and the machine (base + prefix, with the meaning change and a counter of the combinations that do not exist — the manual's dislock / unagree point). The compare card covers un- vs dis-, mis- vs un-, over- vs under-, re- vs un-/dis- and the im- trap; the points-to-watch card is the manual's exception box; the errors card is its pitfall box.
- Build is productive: students assemble words by choosing the prefix for a meaning (exercise A), then transform — typing the prefixed verb a sentence needs, the informal phrasal twin, or the corrected spelling (exercises B, C and D).
- Drill merges the quizzes into one graded engine of 13 items (★ meaning of the prefix & real vs invented word · ★★ spelling and the right prefix · ★★★ im-, tense, and the redo/undo pair) with score, streak and medals.
- Works offline. Reading/writing only — no audio.
Build the word
Read the meaning, then choose the prefix the base word needs. The machine builds it — guess before you check.
Drill — one flow, three levels
★ meaning of the prefix & real vs invented words · ★★ spelling and the right prefix · ★★★ the im- trap, tense and the redo/undo pair. Keep your streak alive. (Igual escalera que tu Cuaderno de tareas.)