Learn Hardcore Spanish (Latin America): Practico el vocabulario en la biblioteca cada día. - I practice the vocabulary in the library every day.

Practico already means I practice (first person singular).
You only add yo for emphasis or contrast, for example:
- Yo practico el vocabulario, pero él no practica nada.
  So Practico el vocabulario… is the most natural, neutral way to say it.

What tense is practico, and why is that tense used here?

Practico is the present indicative, first person singular of practicar. In Spanish, the simple present is normally used for:

Habits and routines: Practico el vocabulario cada día = I practice vocabulary every day.
General truths and ongoing situations.

So we don’t need a special “I do practice” or “I am practicing” form here; the plain present covers the idea of a regular habit.

Could I say Estoy practicando el vocabulario instead? What is the difference?

Yes, Estoy practicando el vocabulario is grammatically correct, but the nuance is different:

Practico el vocabulario cada día = I habitually practice; it’s part of my routine.
Estoy practicando el vocabulario = I am in the middle of practicing right now (present progressive).

With cada día, the simple present (practico) is the natural and expected choice.

Why is it practico and not práctico with an accent?

Accent marks in Spanish can change both pronunciation and meaning.

practico (no accent) = I practice (verb, 1st person singular, present).
práctico (with accent) = practical (adjective) or sometimes I practice in a different stress pattern in some contexts, but in standard modern usage for this meaning, we write practico without an accent.

In this sentence, it’s clearly the verb practico, so it does not take an accent mark.

Why is el used before vocabulario? In English we just say “practice vocabulary,” not “the vocabulary.”

Spanish uses definite articles (el, la, los, las) more often than English, especially with abstract or general nouns.

Practico el vocabulario = I practice the vocabulary (in general / the vocabulary I’m learning).
Leaving out the article (Practico vocabulario) is possible, but it can sound a bit more like “I practice some vocabulary” or “I practice vocabulary (as a type of activity).”

In most everyday contexts, practicar el vocabulario sounds more natural.

Could I say mi vocabulario instead of el vocabulario?

You can say mi vocabulario, but it changes the nuance:

el vocabulario = the vocabulary you’re studying (from your course, book, list, etc.) in a general sense.
mi vocabulario = my personal vocabulary, the set of words I know or use.

So Practico el vocabulario usually refers to the material (lists, units, etc.) you’re working on in class or from a resource.

Why is it en la biblioteca and not something like a la biblioteca?

Prepositions in Spanish don’t always match English exactly.

en la biblioteca = in/at the library (location where the action happens).
a la biblioteca = to the library (movement toward that place).

In this sentence, we’re talking about where you practice, not where you’re going, so en is the correct preposition.

What’s the difference between biblioteca and librería? I thought librería was “library.”

This is a classic false friend:

So if you study in a library, you say en la biblioteca, not en la librería.

Why is it la biblioteca (feminine) and not el biblioteca?

In Spanish, every noun has a grammatical gender that you generally must memorize.

biblioteca ends in -a and is feminine, so it takes la.
That’s why we say la biblioteca, una biblioteca, esta biblioteca, etc.

There isn’t a logical rule that tells you why it’s feminine; you just learn the noun together with its gender.

Can cada día go somewhere else in the sentence, like at the beginning or the end?

Yes, Spanish word order is fairly flexible with time expressions. All of these are correct:

The meaning stays the same; moving cada día can slightly change the emphasis, but all are natural.

What’s the difference between cada día and todos los días?

They both mean every day, and both are common in Latin American Spanish.

cada día = literally each day; can sound a bit more individualizing or slightly more formal or literary in some contexts.
todos los días = literally all the days; very common and fully natural in everyday speech.

You could say Practico el vocabulario en la biblioteca todos los días with essentially the same meaning.

Is practicar regular? How is practico formed?

Yes, practicar is regular in the present tense. For yo, you drop -ar and add -o:

Its present-tense forms are:

The spelling change c → qu happens only in some past forms (like yo practiqué) and does not affect practico.