Learn Hardcore French: Ce vêtement est sale, je dois le laver. - This piece of clothing is dirty, I have to wash it.

vêtement is masculine singular, so the basic form is ce.
cet is used before a masculine singular noun that starts with a vowel or mute h (e.g. cet homme, cet arbre).
cette is for feminine singular nouns (e.g. cette robe).
ces is for all plurals (masculine or feminine) (e.g. ces vêtements, ces robes).

So:

ce vêtement = this/that garment
cet habit (if habit is pronounced with mute h)
cette chemise
ces vêtements

What exactly does vêtement mean? Is it “clothes” or “a piece of clothing”?

Un vêtement is a single item of clothing:

un vêtement = a garment / a piece of clothing

The usual word for clothes (in general) is the plural:

des vêtements = (some) clothes
les vêtements = the clothes

So:

Ce vêtement est sale = This garment / this item of clothing is dirty.
Ces vêtements sont sales = These clothes are dirty.

Why is sale the same form here for a masculine noun? Shouldn’t it change?

Sale is an adjective meaning dirty. It does change with number, but not with gender in the singular:

Masculine singular: un vêtement sale
Feminine singular: une chemise sale
Masculine plural: des vêtements sales
Feminine plural: des chemises sales

So in Ce vêtement est sale, the noun is singular, so the adjective is sale (no s). If it were plural, you’d add an s: Ces vêtements sont sales.

Is the comma in « Ce vêtement est sale, je dois le laver. » correct in French? In English it looks like a comma splice.

In English, joining two full sentences with only a comma is usually considered incorrect.

In French, using a comma between two main clauses like this is very common and acceptable, especially in informal or neutral writing:

Ce vêtement est sale, je dois le laver.

You could also use a conjunction, which sounds slightly more structured:

Ce vêtement est sale, alors je dois le laver. (so)
Ce vêtement est sale, donc je dois le laver. (therefore)

But the simple comma is fine in French.

Why is it je dois le laver and not je dois la laver or je dois les laver?

The pronoun le is a direct object pronoun that replaces a masculine singular noun.

ce vêtement is masculine singular → pronoun: le
cette chemise (feminine singular) → la
ces vêtements (plural) → les

Examples:

Ce vêtement est sale, je dois le laver.
Cette chemise est sale, je dois la laver.
Ces vêtements sont sales, je dois les laver.

So le in this sentence means “it”, referring back to ce vêtement.

Why is the pronoun placed in je dois le laver and not je le dois laver?

With a conjugated verb + infinitive structure in French (like devoir + laver), object pronouns go before the infinitive whose action they receive:

Je dois le laver. (I must wash it.)
Je veux le voir. (I want to see it/him.)
Je peux le faire. (I can do it.)

Je le dois laver is not correct French.

General rule:

Single verb: pronoun goes before the conjugated verb → Je le lave.
Conjugated verb + infinitive: pronoun goes before the infinitive → Je veux le laver.

Could I say je dois laver ça instead of je dois le laver?

You can say je dois laver ça, but it’s a bit more vague and a bit more spoken in tone.

Je dois le laver → “I must wash it”, clearly refers to a specific noun already mentioned (ce vêtement).
Je dois laver ça → “I must wash this/that”, using ça as a demonstrative pronoun; it’s less precise in terms of gender/number and more casual.

In careful, clear French that directly picks up ce vêtement, je dois le laver is the best choice.

Why not use il faut instead of je dois? What’s the difference?

Both express necessity/obligation, but from different angles:

Je dois le laver.
- Uses devoir.
- Literally: I must / I have to wash it.
- Sounds like a personal obligation.
Il faut que je le lave.
- Uses il faut
  - subjunctive (que je le lave).
- Literally: It is necessary that I wash it.
- Often sounds more general or impersonal.

For a simple, everyday obligation about yourself, je dois le laver is very natural and straightforward.

Why is it laver and not se laver here?

laver (without se) = to wash something/someone else
se laver = to wash oneself (reflexive verb)

In the sentence:

Je dois le laver. → I must wash it (the garment).
The object is the garment, not the speaker.

If you were talking about washing yourself, you would use se laver:

Je dois me laver. → I must wash (myself).

Can I drop the subject pronoun and just say dois le laver like in Spanish?

No. In standard French, you cannot normally drop the subject pronoun. The subject pronoun is almost always required:

Je dois le laver. ✅
Dois le laver. ❌ (sounds incomplete or like a fragment)

French verbs do not clearly show the subject in the same way as in Spanish or Italian, so the subject pronoun is needed for clarity and is part of normal grammar.

How do you pronounce vêtement and what does the ê change?

vêtement is pronounced approximately: /vɛt.mɑ̃/

vêt- → vɛt, like “vet” in English, but with a pure ɛ sound.
-ement in this word → -mɑ̃ (the e is not pronounced, -ent is silent, and -m nasalizes the vowel).
The ê (accent circonflexe) indicates a “wide” open e sound /ɛ/ (like in tête) and often historically marks a missing s (vêtement ← vestiment / veste family).

So you do not pronounce something like “vet-e-mont”; it’s more like vɛt-mɑ̃.

If I want to say “These clothes are dirty, I must wash them”, how would I change the sentence?

You need the plural forms:

Ces vêtements sont sales, je dois les laver.

Changes:

Ce → Ces (plural demonstrative)
vêtement → vêtements (add s)
est → sont (3rd person plural of être)
sale → sales (add s for plural)
le → les (direct object pronoun for plural)

So the full plural version is: Ces vêtements sont sales, je dois les laver.