The Spanish neuter article "lo" can refer to something that has been mentioned before as a clause, a verb or an adjective. For example:
Tenías que disculparte pero no lo hiciste.You were supposed to apologise but you didn't do it.
Sabes que la pastilla para el abuelo toca a las 12; ¿Lo recordarás?You know that grandpa is due to take his pill 12; Will you remember (it)?
No parece muy contento pero yo sé que lo está.He doesn't look very happy but I know he is.
When we have a sentence using estar + adverb like bien or mal, "lo" can also be used to refer to that adverb, for example:
-¿Estás bien, cariño? -Sí, lo estoy, mamá, no te preocupes.-Are you OK, honey? -Yes, I am, mum, don't worry.
-No quiero que estés mal por mi culpa. -Tranquilo, no lo estaré.-I don't want you to feel bad because of me. -Don't worry, I won't (feel bad).
Remember that in translation, the English may not use the article "it" because it's not always required in every case, but in Spanish we always use it.
Lo is invariable. Even if it replaces an adjective in the feminine form, it remains lo (not la). Have a look:
-Dicen que la chica es muy guapa. -No, no lo es.
-Dicen que la chica es muy guapa. -No, no la es.
They say the girl is very pretty. -No, she isn't.
It is important to remember that the use of "lo" is compulsory in these cases. You cannot decide not to use it and leave the verb with no article even though this is possible in some cases in English:
-¿Estás bien? -Sí, lo estoy.
-¿Estás bien? -Sí, estoy.
Are you OK? -Yes, I am.
For other uses of the neuter article lo see:
Remember that "lo" can also be a direct object pronoun:
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