Once you have the basic lo bueno / lo importante pattern in your repertoire, three advanced uses of lo open up. They are responsible for some of the most expressive — and uniquely Spanish — sentences you'll read or hear: the intensifier construction lo + adjective + que ("how X..."), the relative lo cual that refers back to a whole clause, and the relative lo que that refers to content. Combined, these are what let you build the elegant emphatic and explanatory sentences that mark a B2/C1 speaker.
This page assumes you've already met the basic neuter article on the neuter-lo page. Here we go further: how lo becomes an intensifier, how it picks up clauses as antecedents, and how it powers cleft sentences.
The intensifier: lo + adjective/adverb + que + verb
This is the headline construction. It looks innocuous, but it does work that English needs how + adjective + clause for, and Spanish does it more naturally and in more contexts.
No te imaginas lo cansado que estoy después de la mudanza.
You can't imagine how tired I am after the move.
¡Lo bonita que es esta ciudad cuando no hay turistas!
How beautiful this city is when there are no tourists!
Me sorprende lo bien que habla español tu hermano, ¿dónde lo aprendió?
I'm surprised at how well your brother speaks Spanish — where did he learn?
The structure has four slots:
|
|
|
|
|---|---|---|---|
| lo | cansado | que | estoy |
| lo | bien | que | canta |
| lo | poco | que | duerme el bebé |
A crucial twist that breaks the basic lo bueno rule: when the adjective in slot 2 is describing a specific person or thing, it agrees with that referent in gender and number — not with the default masculine singular.
No sabes lo cansada que estoy después de toda la semana.
You don't know how tired I am (woman speaking). — cansada, feminine, agreeing with the speaker.
Lo simpáticos que son tus padres, de verdad — me han tratado de maravilla.
Your parents are so lovely, really — they've treated me wonderfully. — simpáticos, masculine plural, agreeing with tus padres.
¡Lo guapas que están tus hijas en la foto!
How beautiful your daughters look in the photo! — guapas, feminine plural.
This agreement is the key feature distinguishing the intensifier from the basic lo + adjective abstract pattern. In lo bueno de la casa, the adjective is invariably masculine singular. In lo guapas que están tus hijas, it agrees with whatever specific entity it modifies. Same word lo, completely different operation.
When lo is followed by an adverb instead of an adjective, there's no agreement question — adverbs don't agree:
No te imaginas lo rápido que pasa el tiempo cuando uno tiene hijos.
You can't imagine how fast time goes when you have kids.
Es increíble lo mal que conduce, y eso que lleva veinte años con el carné.
It's incredible how badly he drives, even though he's had his licence for twenty years.
When the construction is exclamatory vs embedded
The same structure works in two registers — as a freestanding exclamation, and as an embedded clause inside a larger sentence.
Freestanding exclamation — opens with ¡ and closes with !, usually emotional:
¡Lo orgullosos que estamos de ti, hijo!
How proud we are of you, son!
¡Lo tarde que es y todavía no he cenado!
How late it is and I still haven't had dinner!
Embedded — appears after a main verb that takes a complement (saber, ver, imaginar, sorprender, creer, no te imaginas, te juro, etc.):
Te juro que no sabes lo difícil que ha sido encontrar piso en esta zona.
I swear, you don't know how hard it's been to find a flat in this area.
Me alegro de ver lo bien que te llevas con su familia.
I'm glad to see how well you get along with his/her family.
The embedded version is enormously common in everyday Spanish after no te imaginas, no te creerías, vas a ver — all conversational openers.
Lo cual — referring back to an entire clause
The second advanced use: lo cual functions as a relative pronoun whose antecedent is not a noun but an entire preceding clause. The English equivalent is which, used with a comma to comment on what was just said.
No vino a la reunión, lo cual me sorprendió bastante.
He didn't come to the meeting, which surprised me quite a bit.
Han subido los precios otra vez, lo cual era previsible dada la inflación.
They've raised prices again, which was predictable given the inflation.
Decidió dejar el trabajo y mudarse al campo, lo cual nadie esperaba.
He decided to quit his job and move to the countryside, which nobody expected.
What lo cual refers to in these sentences is not a single noun — it's the entire propositional content of the previous clause. Lo cual me sorprendió doesn't mean "the X that surprised me" for any specific X; it means "the whole fact that he didn't come, which surprised me." This is exactly what English which does in non-restrictive relative clauses.
Lo cual belongs to the slightly more formal register. In casual speech, lo que often replaces it (see below), or speakers restructure: No vino, y eso me sorprendió.
Lo cual is also the natural choice after a preposition:
No me devolvió las llaves, por lo cual tuve que cambiar la cerradura.
He didn't give me the keys back, for which reason I had to change the lock.
Llegó tarde y sin avisar, ante lo cual mi madre se enfadó muchísimo.
He arrived late and without warning, in the face of which my mother got extremely angry.
The fixed combinations por lo cual (for which reason), ante lo cual (in the face of which), con lo cual (so / which means), tras lo cual (after which) are journalistic and academic staples.
Lo que — referring to content
Lo que is a relative pronoun too, but its antecedent is different. Where lo cual points back to an entire preceding clause, lo que refers to abstract content — a thing, an idea, a situation — and it can also stand at the beginning of a sentence, with no antecedent at all.
No sé lo que quiere, nunca lo dice claramente.
I don't know what he wants — he never says it clearly. — lo que = the thing he wants.
Lo que más me molesta es que no se disculpe nunca.
What bothers me most is that he never apologizes. — lo que opens the sentence, referring to abstract content.
Dime lo que piensas, en serio, no te voy a juzgar.
Tell me what you think, seriously, I won't judge you.
This is the what of "I know what you want" or "what bothers me is..." — it bundles up an abstract object inside a relative clause. When the antecedent is a whole clause already mentioned, both lo cual and lo que can appear, with a register difference:
Subieron los precios, lo que / lo cual me parece injusto.
They raised the prices, which seems unfair to me. — lo que (everyday) or lo cual (more formal/written). Both correct here.
The rules of thumb:
- At the beginning of a sentence (with no preceding clause as antecedent), only lo que is possible: Lo que necesito es café (what I need is coffee), never lo cual necesito.
- As the object of a verb with an abstract referent: no sé lo que dice. Again, only lo que.
- After a comma, referring back to a whole clause: both lo que (informal/everyday) and lo cual (formal/written) work.
- After a preposition referring to a whole clause: lo cual is the more formal choice — por lo cual, ante lo cual, tras lo cual. In everyday speech, por lo que is just as common and equally correct (no me devolvió las llaves, por lo que tuve que cambiar la cerradura). The fixed ante lo cual and tras lo cual combinations, on the other hand, don't have everyday que equivalents.
Cleft sentences with lo que
One of the most powerful ways lo que gets used is in cleft sentences — sentences that take a chunk of information and isolate it for emphasis. The English equivalent uses what...is...: What I need is silence, What matters is your effort.
Lo que importa es que vengas, da igual a qué hora.
What matters is that you come — it doesn't matter what time.
Lo que nadie se esperaba era que el ministro dimitiera en directo.
What nobody expected was that the minister would resign live on air.
Lo que necesito ahora es un café bien cargado y diez minutos de silencio.
What I need right now is a really strong coffee and ten minutes of silence.
The pattern is lo que + verb (+ rest) + ser + the highlighted information. The ser (in the indicative for facts, or subjunctive for desired situations) bridges the two halves. Cleft sentences with lo que are pervasive in Spanish — far more common than English clefts — because they let you reorder information for emphasis without a heavy syntactic detour.
Lo que pasa es que is worth memorizing as a unit — the standard Spanish equivalent of English "the thing is" or "what's happening is," used dozens of times in any extended conversation:
Lo que pasa es que mi madre se preocupa por todo, incluso por tonterías.
The thing is, my mother worries about everything, even silly things.
Lo cual vs lo que — the cleanest test
When in doubt, ask: does the relative point back to a previously mentioned whole clause (formal context), or does it refer to abstract content (general use)?
| Context | Use | Example |
|---|---|---|
| Refers to a noun (specific thing) | que / el que / el cual | el libro que compré |
| Refers to abstract content (no antecedent) | lo que | lo que necesito es paz |
| Refers back to a whole clause, informal | lo que | no vino, lo que me sorprendió |
| Refers back to a whole clause, formal | lo cual | no vino, lo cual me sorprendió |
| After preposition, refers to whole clause | lo cual | por lo cual tuve que volver |
| At the start of the sentence | lo que | lo que importa es... |
Lo with a possessive — lo mío, lo tuyo, lo suyo
Lo + a possessive creates an abstract noun phrase meaning "my/your/his/her thing," "the matter with X."
Lo suyo es la cocina, dejémosle hacer la cena.
Cooking is his thing — let him do dinner.
No te metas en lo nuestro, es un asunto entre mi marido y yo.
Don't get involved in our business — it's between my husband and me.
The phrase is tonally rich: lo suyo often means "the thing he's good at"; lo nuestro in romantic contexts means "our relationship" (lo nuestro se acabó = it's over between us); lo mío signals personal taste or domain (lo mío es la lectura, reading is my thing).
Common Mistakes
❌ No te imaginas lo cansado que está mi hermana.
If hermana is the subject of está, the adjective must agree: cansada, not cansado.
✅ No te imaginas lo cansada que está mi hermana.
You can't imagine how tired my sister is. — agreement with the feminine subject.
❌ Lo cual necesito es un descanso.
At the start of a sentence with no antecedent, lo cual is impossible — only lo que works.
✅ Lo que necesito es un descanso.
What I need is a rest. — lo que opens cleft and content-relative sentences.
❌ No vino, que me sorprendió.
Que alone cannot refer back to a whole clause — you need lo que or lo cual.
✅ No vino, lo que / lo cual me sorprendió.
He didn't come, which surprised me. — lo que (everyday) or lo cual (formal).
❌ ¡Lo bonita es esta ciudad!
The intensifier construction needs que + verb: lo + adj + que + verb. Without que, the sentence is incomplete.
✅ ¡Lo bonita que es esta ciudad!
How beautiful this city is! — the obligatory que links the adjective to the verb.
❌ ¡Qué cansado que estoy!
The intensifier with que + verb is built on lo, not qué. ¡Qué cansado estoy! (without que) is fine as a regular exclamation; the lo + adj + que + verb pattern requires lo.
✅ ¡Lo cansado que estoy! / ¡Qué cansado estoy!
How tired I am! — both are correct exclamations, but only the lo... que... pattern licenses the embedded version (no sabes lo cansado que estoy).
Key takeaways
- Lo + adjective/adverb + que + verb is the Spanish intensifier — no sabes lo cansado que estoy. The adjective agrees with the referent's gender and number, unlike the basic lo bueno abstract pattern.
- The intensifier works both as a freestanding exclamation (¡lo bonita que es!) and embedded after verbs of perception (me sorprende lo bien que canta).
- Lo cual is a relative pronoun whose antecedent is an entire preceding clause. It belongs to formal and written Spanish, and is the only choice after prepositions (por lo cual, ante lo cual).
- Lo que refers to abstract content. It can stand at the start of a sentence with no antecedent (lo que necesito es...), function as the object of verbs (no sé lo que quiere), or replace lo cual in everyday register when referring to a previous clause.
- Cleft sentences built on lo que + verb + ser + X are the standard Spanish way to foreground information for emphasis — lo que importa es que vengas. Far more common than English clefts.
- Lo + possessive (lo mío, lo tuyo, lo nuestro) packages a personal domain or relationship into a noun phrase, with tonal range from neutral (lo suyo es la cocina) to charged (lo nuestro se acabó).
- The internal logic of all advanced lo uses is the same as the basic neuter article: lo points to abstraction, content, or a whole stretch of meaning, never to a single concrete entity.
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Start learning Spanish→Related Topics
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