Eu respondi‑lhe que “lhe” é um pronome, e todos riram.

Lhe is an unstressed indirect‑object pronoun meaning to him / to her / to you (formal) in the singular.

• It usually replaces a ele, a ela, ao senhor, à senhora, a você, etc.
• So eu respondi‑lhe ≈ eu respondi a ele / a ela (“I answered him / her” or more naturally in English: “I told him / her”).
• It does not distinguish gender; context tells you if it’s “him” or “her”.

In European Portuguese, unstressed object pronouns normally attach to the verb with a hyphen in neutral affirmative sentences. This is called enclisis.

• Pattern in European Portuguese: [verb]‑[pronoun] → respondi‑lhe, dei‑lhe, mostrei‑lhe.
• You write the pronoun together with the verb, connected by a hyphen.
• Writing respondi lhe (without hyphen) is incorrect.

In European Portuguese, Eu lhe respondi (pronoun before the verb in this context) sounds wrong or at least very unnatural.

• The normal form is Eu respondi‑lhe.
• Pronoun before the verb (proclisis, e.g. lhe respondi) only appears when certain “attracting” words are present (like não, que, se, etc.):
  
  • Não lhe respondi.
  • Quando lhe respondi, todos riram.
• The pattern subject + lhe + verb (Eu lhe respondi) is typical of Brazilian Portuguese, not European Portuguese.

Because the verb responder works differently in Portuguese than to answer in English.

• In Portuguese, you responder a alguém (“answer to someone”):
  
  • Respondi a ele. → indirect object with a
  • Respondi‑lhe. → same thing, but with clitic pronoun lhe
• Respondi ele is ungrammatical in standard Portuguese.
• Respondi-o would mean “I answered it / him” only if “he / it” is the thing answered (a question, an email, etc.), but that’s not how responder is usually used; you more often say:
  
  • Respondi à pergunta. / Respondi ao e‑mail.
    not respondi‑a or respondi‑o in everyday speech.

Here que is a complementizer – roughly “that” in English.

• Structure: responder (a alguém) que… → “to answer (someone) that…”
• It introduces the whole clause lhe é um pronome as the content of what was answered.
• English equivalent: “I answered him that lhe is a pronoun …”, or more natural: “I told him that lhe is a pronoun …”.

É is used because being “a pronoun” is a timeless fact, not something that was only true in the past.

• In indirect/reported speech, Portuguese often keeps the present tense when the statement is still true at the time of speaking:
  
  • Respondi‑lhe que Lisboa é a capital de Portugal.
    (“I told him Lisbon is the capital of Portugal.” — still true)
• You might use era if you were talking about something that was true then but is no longer true now, which doesn’t fit “lhe is a pronoun”.

Yes, you can absolutely omit Eu: Respondi‑lhe que lhe é um pronome, e todos riram.

• In Portuguese, the verb ending (‑i in respondi) already tells you the subject is “I”, so Eu is optional.
• Including Eu can add a bit of emphasis or clarity, especially in longer contexts, but grammatically it’s not required.

Portuguese comma rules are not identical to English ones, and a comma before e is more acceptable.

• Here we have two independent clauses:
  • Eu respondi‑lhe que lhe é um pronome
  • todos riram
• Linking them with , e to mark a clearer pause or slight change of focus is quite natural in Portuguese.
• In English, you’d usually write: “… and everyone laughed.” without the comma, but in Portuguese “… , e todos riram.” is fine (though “… e todos riram.” without the comma would also be acceptable).

Todos riram can mean either “everyone laughed” or “they all laughed”, depending on context.

• Todos is a pronoun here, standing for some previously known group.
• If you want to be more explicit you can say:
  • Todos eles riram. – “They all laughed.”
  • Toda a gente riu. – “Everybody laughed.”
• Without extra words, todos riram simply refers to all the relevant people in the situation that has already been mentioned or is obvious.

Both rir and rir‑se are used in European Portuguese, often with very similar meanings.

• Todos riram. – perfectly natural: “Everyone laughed.”
• Todos se riram. – also possible; in many contexts it doesn’t change the meaning much.
• There are some subtler patterns of use:
  • rir tends to be a bit more neutral and common in everyday narration.
  • rir‑se de can emphasize laughing at someone/something:
    
    • Todos se riram dele. – “They all laughed at him.”
• In your sentence, e todos riram is the most straightforward choice.

The two lhe’s have different functions:

1. respondi‑lhe – lhe is an indirect object pronoun: “I answered him/her”.
2. que “lhe” é um pronome – here lhe is being mentioned as a word, not used as a pronoun in the sentence’s grammar. You’re talking about the word lhe itself.

In writing, you normally show this by putting the word being mentioned in quotation marks or italics, as in que “lhe” é um pronome or que lhe é um pronome.

Lhe is singular only; it refers to one person (or one entity) in the third person.

• For the plural, you use lhes:
  • Respondi‑lhes que lhe é um pronome. – “I told them that lhe is a pronoun.”
• So:
  • lhe → “to him / to her / to you (formal, singular)”
  • lhes → “to them / to you (formal, plural)”