Revisamos la dureza del agua.

Revisamos is the first-person plural form of revisar, so it means we check / we review / we inspect.

One important detail: this form is also identical to the preterite form, so out of context revisamos can mean either we check or we checked. Context normally makes it clear.

Spanish usually leaves out subject pronouns when the verb ending already shows who is doing the action. The ending -amos already tells you the subject is we.

You could say Nosotros revisamos la dureza del agua, but that would usually sound more emphatic, contrastive, or clearer in a context where the subject needs to be stated.

Not usually in the English sense of editing or rewriting a text. In Spanish, revisar often means to check, to inspect, to examine, or to go over something.

So in this sentence, revisamos is more like we check or we inspect, not we revise.

Spanish often uses the definite article with abstract nouns and known concepts where English might not. Here, la dureza refers to the specific property being checked: the hardness.

So la dureza del agua is the natural way to say the hardness of the water or water hardness.

Because de + el contracts to del in normal Spanish. So:

• de + el = del

That is why you get la dureza del agua.

Yes, agua is a feminine noun. However, singular feminine nouns that begin with a stressed a- or ha- sound often use el instead of la for pronunciation reasons.

So you say:

• el agua
• el águila

But the noun is still feminine, which you can see in adjectives:

• el agua fría
• el agua limpia

So del agua is correct because it comes from de + el agua.

Spanish usually does not join nouns together the way English often does. English easily makes noun combinations like water hardness, car door, or coffee cup.

Spanish usually prefers noun + de + noun, so la dureza del agua is the normal structure.

In most of Spain, dureza is pronounced roughly like doo-RE-tha, because the z is pronounced like the th in thin.

So the sentence sounds approximately like:

reh-bee-SAH-mos la doo-RE-tha del AH-gwa

Also note that in Spanish, v and b are pronounced very similarly, so revisamos does not sound like English revise.

Yes. The Spanish present tense can often express both a general action and something happening right now, depending on context.

So Revisamos la dureza del agua can mean:

• We check the water hardness
• We are checking the water hardness

If you want to make the ongoing action more explicit, you can say Estamos revisando la dureza del agua.

Dureza is a noun, formed from the adjective duro / dura meaning hard. The ending -eza is one way Spanish forms abstract nouns, similar to English endings like -ness.

So:

• duro = hard
• dureza = hardness