The comma switch: defining vs non-defining
A relative clause gives more information about a noun, joining two ideas into one smoother sentence. A defining clause identifies which one — essential information, no commas. A non-defining clause adds extra information about something already identified — always inside commas, and never with that. Flip the switch and watch the meaning change. (Sin comas = identifica cuál; con comas = solo añade un dato.)
1 · Choose a sentence
2 · Flip the comma switch
Who, which, that, whose, where, when — and whom
Tap a pronoun to see what it is used for, an example, and why it is the right choice there. (El pronombre depende del sustantivo: persona, cosa, posesión, lugar o tiempo.)
Drop it only when it is the object (defining clauses)
Choose a phrase, then try to drop the pronoun. Quick test: is there a subject (we, they, I, a noun) right after the pronoun? Yes → the pronoun is the object → optional. No → it is the subject → keep it. Whose is never dropped. (Solo se omite el pronombre objeto, y solo sin comas.)
That in commas, prepositions, where vs which…
Spot the mistake, then tap to reveal the fix
Each sentence has one typical error. Decide what is wrong first — guess before you check. (Errores frecuentes por influencia del español.)
👩🏫 For the teacher — how this page maps to the manual
- Explore is Grammar 8's "big divide": the comma switch shows the same sentence as defining (no commas, it narrows the set) and non-defining (commas, it adds a fact about the whole set), including a proper name that can only be non-defining and that → which inside commas. The pronoun chooser is the six-row table (plus formal whom); the omission card is exercise D; the special-cases card is the exceptions box (that in commas, prepositions, whole-idea which, where/when vs which, whose for things); the errors card is the pitfall box plus the error hunt of Task set 12.
- Build is productive: students assemble a sentence by choosing the pronoun and deciding on the commas (exercises A and C), then transform pairs of sentences into one (exercise B), with validation, a comma check and a model answer.
- Drill is one graded engine (★ pronoun choice & commas · ★★ fix the error & drop the pronoun · ★★★ where vs which, the meaning of the commas, whole-idea which, fronted preposition) with a score and streak.
- Works offline. Reading/writing only — no audio.
Build a relative clause
Read the sentence, choose the relative pronoun and decide whether the clause needs commas. The machine joins it — guess before you check.
Drill — one flow, three levels
★ choose the pronoun & the commas · ★★ fix the error & drop the pronoun · ★★★ where vs which, meaning, whole-idea which, formal prepositions. Keep your streak alive. (Igual escalera que tu Cuaderno de tareas.)