Learn Hardcore Spanish (Latin America): Por favor, trapea la sala antes de la cena. - Please mop the living room before dinner.

Yes. Trapea is the affirmative command for tú (informal “you”). For regular -ar verbs, the affirmative tú command matches the 3rd-person singular of the present indicative: él/ella trapea → (tú) trapea.

How do I say it formally or to more than one person (and what about voseo or Spain)?

Formal (usted): Por favor, trapee la sala antes de la cena.
Plural (ustedes, used across Latin America): Por favor, trapeen la sala antes de la cena.
Voseo (Argentina, Uruguay, Paraguay, most of Central America, parts of Bolivia/Chile): Por favor, trapeá la sala antes de la cena.
Spain (vosotros): Por favor, trapead la sala antes de la cena.

How do I make it negative?

Negative commands use the present subjunctive:

Tú: No trapees la sala antes de la cena.
Usted: No trapee la sala…
Ustedes: No trapeen la sala…
Vos: No trapeés la sala…
Vosotros (Spain): No trapeéis la sala…

What exactly does "la sala" refer to? Is it the living room?

Yes. In most of Latin America, la sala means “the living room” (also la sala de estar). In Spain, you often hear el salón. Note that sala can also mean “room” in compounds like sala de emergencias (emergency room).

Why is it "la sala" and "la cena" with articles? Can I drop them?

With rooms, Spanish normally uses the definite article: trapea la sala (not “trapea sala”).
With meals, Spanish commonly uses the article when referring to the meal as an event: antes de la cena, después del almuerzo.
You can avoid the article by using an infinitive instead of a noun: antes de cenar is also natural.

Why "antes de"? When do I use "antes de," "antes de que," or an infinitive?

Before a noun: antes de + noun → antes de la cena.
Before a verb when the subject is the same as the main clause: antes de + infinitive → antes de cenar.
Before a full clause with its own subject: antes de que + subjunctive → antes de que cenemos (“before we have dinner”).

Is "antes que" ever correct?

As a temporal connector, antes de que is the standard choice (e.g., antes de que llegues). Antes que is also accepted before a clause in many varieties, but less formal; avoid it before nouns.
Do not say antes que la cena. Say antes de la cena or antes de cenar.
In comparisons/preferences, antes que is normal: Prefiero trapear antes que barrer.

Where should "por favor" go, and do I need a comma?

You can place por favor at the start or end (or even in the middle) and set it off with commas:

Por favor, trapea la sala antes de la cena.
Trapea la sala antes de la cena, por favor.
Trapea, por favor, la sala antes de la cena. Capitalize Por only if it starts the sentence.

How do I add pronouns like "it" to avoid repeating "la sala"?

Affirmative commands attach pronouns at the end and keep the original stress with an accent:
- Trapéala antes de la cena. (= Trapea la sala…)
- With two pronouns (indirect + direct): Trapeámela antes de la cena. (me + la)
Negative commands put pronouns before the verb:
- No la trapees antes de la cena. Order with two pronouns: indirect (me/te/le/se/nos/les) + direct (lo/la/los/las).

What’s the difference between "trapear," "barrer," "fregar," and "limpiar"?

Trapear = to mop (use a mop and water/cleaner).
Barrer = to sweep (with a broom).
Fregar = to scrub/wash. In Spain, fregar el suelo often means “to mop the floor.” In much of Latin America, fregar is not the usual verb for mopping floors.
Limpiar = to clean (general). You can say limpia la sala, but it’s less specific than trapea.
For vacuuming: pasar la aspiradora.

Are there regional words I should know for "mop" or "to mop"?

“Mop” (noun): trapeador (widely in Latin America), fregona (Spain), mopa (Spain; also used in some countries for a flat mop/dust mop), lampazo (Argentina/Uruguay), coleto (Venezuela), mapo (Puerto Rico/Dominican Rep., colloquial).
“To mop”: trapear (widely in Latin America), fregar el suelo / pasar la fregona (Spain), mapear (PR/DR, colloquial).
When in doubt in Latin America, trapear and trapeador are safe choices.

Could I say "Trapea el piso" or "Trapea el suelo" instead?

Yes:

piso = “floor” in most of Latin America; in Spain it can also mean “apartment.”
suelo = “floor/ground” everywhere.
So you can say Trapea el piso de la sala or Trapea el suelo, though Trapea la sala is also natural because the floor is implied.

How is everything pronounced?

Por favor: [poɾ faˈβoɾ] (the “r” is a quick tap; “v” sounds like a soft “b”).
trapea: [tɾaˈpea] (three syllables: tra-PE-a; the “ea” are two separate vowels).
la sala: [la ˈsala].
antes de: [ˈantes de].
la cena: [la ˈsena] in Latin America (like “seh-nah”); in most of Spain, the “c” before “e” is ˈθena].
Stress falls on the capitalized part above: tra-PE-a, SA-la, CE-na.

Is "trapear" a regular verb? How do I conjugate it in common tenses?

Yes, it’s regular.

Present: yo trapeo, tú trapeas, él/ella trapea, nosotros trapeamos, ellos trapean
Preterite: yo trapeé, tú trapeaste, él/ella trapeó, nosotros trapeamos, ellos trapearon
Present subjunctive (used for negatives/requests): (que) yo trapee, tú trapees, él/ella trapee, nosotros trapeemos, ellos trapeen
Gerund/participle: trapeando / trapeado

Is there a softer/more polite way than using an imperative?

Yes. Options include:

¿Podrías trapear la sala antes de la cena, por favor?
¿Puedes trapear la sala antes de la cena, por favor?
¿Le podría (usted) trapear la sala antes de la cena, por favor? (formal)
Te encargo que trapees la sala antes de la cena.
¿Me ayudas a trapear la sala antes de la cena?