Learn Hardcore Spanish (Latin America): Lavo el vaso con agua fría.

Spanish verbs are conjugated to show who performs the action. Here, lavo already tells you the subject is “I” (first person). Including yo is optional and would only be for emphasis or contrast.

What does lavo mean, and how is it formed?

Lavo is the first-person singular present tense of the verb lavar (“to wash”). The ending -o signals that the subject is “I,” so lavo literally means “I wash.”

Why do we say el vaso instead of un vaso?

Using el (“the”) indicates you’re talking about a specific glass—perhaps the one you just used. If you said un vaso, it would mean “a glass” in general, not one in particular.

Why is it con agua fría and not en agua fría or con el agua fría?

con expresses the means or tool: “with cold water.”
We drop the article before agua fría because you’re referring to some cold water in general (an uncountable amount), not a specific water.
en agua fría would imply the glass is sitting “in” cold water, rather than you washing it using cold water.

Why is the adjective fría placed after the noun agua?

In Spanish, descriptive adjectives normally follow the noun: agua fría (“water cold”). Only certain adjectives move before the noun for stylistic or emphatic reasons (e.g., gran hombre).

Why isn’t agua treated as masculine since it starts with an “a” sound and sometimes takes el?

Agua is grammatically feminine, but feminine nouns beginning with a stressed “a” or “ha” (like agua, alma) take el instead of la in the singular to avoid the awkward “la agua.” The adjective still agrees in feminine form (fría).

Could I use fregar or limpiar instead of lavar for washing a glass?

Lavar is the standard verb in Latin America for washing dishes and glasses.
Fregar (“to scrub”) is common in Spain but less so in Latin America.
Limpiar means “to clean” more generally and could work, but lavar specifically emphasizes washing with water.

How would you say “I rinse the glass with cold water” instead of “I wash the glass”?

Use enjuagar for “to rinse.” The sentence becomes Enjuago el vaso con agua fría, which means you’re rinsing off soap or residue rather than doing a full wash.