Learn Hardcore Spanish (Latin America): Uso la pieza para arreglar mi bicicleta.

Uso is the first-person singular present indicative form of the verb usar, which means “to use.” In English, it corresponds to “I use.” You conjugate it as uso because the subject (understood) is “yo” (I).

Why is there a definite article la before pieza instead of una or nothing at all?

Spanish typically uses definite articles to talk about specific things:

la pieza = “the piece/part” (a particular one the speaker has in mind)
una pieza = “a piece/part” (any one, not specified)
Omitting the article (uso pieza) sounds unnatural because Spanish generally requires an article before singular countable nouns.

What’s the difference between pieza and parte?

Both pieza and parte can translate as “part,” but:

pieza often refers to a discrete piece or component (e.g., a gear, a bolt).
parte is more general, meaning a portion or section of something (e.g., the front part, a part of a story).
In mechanical contexts, pieza is very common for individual components.

Why is pieza feminine? How do I know its gender?

Nouns ending in -a are usually feminine in Spanish. Pieza ends in -a, so it takes feminine articles and adjectives (la pieza, una pieza, la pieza pequeña).

Why do we use para arreglar instead of just arreglo or arreglando?

para + infinitive expresses purpose: “in order to fix.”
arreglo (I fix) would turn it into a new verb clause: “I fix my bicycle with the piece,” which changes the meaning.
arreglando (fixing) would be a gerund: “I use the piece while fixing my bicycle,” emphasizing simultaneity, not purpose.

Could I use por instead of para to express “in order to”?

No.

para
- infinitive = purpose (“in order to fix”).
por indicates cause, reason, duration, or means (“because of,” “through,” “for a period of time”).
Using por arreglar would sound like “because of fixing,” which doesn’t match “in order to fix.”

What’s the nuance between arreglar, reparar, and componer?

All three can mean “to fix/repair,” but:

arreglar = general “to fix” or “to sort out.”
reparar = specifically “to repair,” often technical or formal.
componer = “to compose” or “to put together,” also used for “to repair” (especially with machines).
In everyday speech, arreglar la bicicleta is most common.

Can I replace arreglar mi bicicleta with arreglarla? If so, how?

Yes. You attach the direct-object pronoun la (for bicicleta) to the infinitive:

Original: Uso la pieza para arreglar mi bicicleta.
With pronoun: Uso la pieza para arreglarla.
Both mean “I use the piece to fix it.”