Learn Hardcore Portuguese (Portugal): Ontem reparei em muito lixo na rua. - Yesterday I noticed a lot of trash in the street.

Ontem = yesterday
reparei = I noticed / I observed (1st person singular, past tense of reparar)
em = in / on (here it’s part of the verb pattern reparar em, “to notice”)
muito = a lot of / much
lixo = trash / rubbish / garbage
na = in the / on the (em
- a, i.e. “in/on the” feminine singular)
rua = street

So a close literal version would be: Yesterday I-noticed in much trash in-the street, which we naturally render in English as: Yesterday I noticed a lot of trash on the street.

Why is the verb reparei em used instead of something like vi for “I saw”?

In European Portuguese:

ver = to see (simple visual perception)
- Ontem vi muito lixo na rua = Yesterday I saw a lot of trash on the street.
reparar em = to notice / to pay attention to / to take note of
- Ontem reparei em muito lixo na rua = you not only saw it but registered it, paid attention to it, maybe found it noteworthy or surprising.

So reparei em suggests a bit more awareness or attention than vi. Both are correct; the nuance is that reparar em focuses on noticing, ver on seeing.

Why do we say reparar em and not just reparar without a preposition?

In European Portuguese, the common structure is:

reparar em algo = to notice something

So:

reparar em muito lixo = to notice a lot of trash.

The preposition em here is part of the verb’s pattern, not a separate idea like “in”. If you drop em and say reparar muito lixo, it sounds wrong or at least very odd in this sense.

There is another use of reparar:

reparar algo = to repair/fix something
- reparar o carro = to fix the car

So:

reparar em X → to notice X
reparar X → to repair X

That em is essential for the “notice” meaning.

What tense is reparei, and how would the full verb reparar be conjugated in that tense?

Reparei is 1st person singular of the pretérito perfeito (simple past), used for completed actions in the past.

Pretérito perfeito of reparar:

eu reparei – I noticed
tu reparaste – you noticed (informal singular, used in Portugal)
ele / ela / você reparou – he / she / you (formal) noticed
nós reparamos – we noticed
vocês / eles / elas repararam – you (plural) / they noticed

So Ontem reparei… = Yesterday I noticed…

Could we say Ontem eu reparei em muito lixo na rua? Is eu necessary?

Yes, you can say:

Ontem eu reparei em muito lixo na rua.

But in Portuguese, the subject pronoun (eu, tu, ele, etc.) is often omitted because the verb ending already shows who the subject is. Reparei can only be eu (I), so eu is not needed unless you want to emphasize:

Ontem EU reparei em muito lixo na rua (mas tu não).
Yesterday I noticed a lot of trash on the street (but you didn’t).

In the neutral, non‑emphatic version, Ontem reparei… is more natural.

Can the word ontem go in another position, like at the end of the sentence?

Yes. Some common options:

Ontem reparei em muito lixo na rua.
Reparei em muito lixo na rua ontem.
Ontem, reparei em muito lixo na rua. (with comma, a bit more formal/written style)

All are correct. Putting ontem at the very beginning is very common when you want to set the time frame first. At the end (…na rua ontem) is also perfectly natural.

What you generally wouldn’t say is splitting the verb and the preposition:

✗ Reparei ontem em muito lixo na rua. – This is not totally impossible, but it sounds a bit clumsy because reparar em likes to stay together. The earlier two versions are better.

Why is it muito lixo and not muitos lixos?

Lixo (trash/rubbish) is usually treated as an uncountable noun in Portuguese, like water or furniture in English.

muito lixo = a lot of trash (mass/uncountable)
pouco lixo = little trash

You normally don’t say muitos lixos to mean “a lot of trash” in a general sense; that sounds odd, like you are counting different kinds of trash.

The plural lixos does exist, but it’s used in more specific or figurative ways, for example:

os lixos recicláveis = recyclable wastes
esses lixos de programas de TV = those trashy TV shows

For what you say in English as “a lot of trash”, the natural expression is muito lixo (singular).

How does muito change with gender and number? Why is it muito here and not muita?

Muito agrees with the noun it modifies:

masculine singular: muito lixo
feminine singular: muita água (a lot of water)
masculine plural: muitos carros (many cars)
feminine plural: muitas pessoas (many people)

Here the noun lixo is masculine singular, so muito stays masculine singular: muito lixo.

If the noun were feminine, like sujidade (dirtiness/dirt), you would say:

muita sujidade na rua = a lot of dirt in the street

Why is it na rua and not em a rua? What exactly is na?

Na is a contraction of the preposition em + the feminine singular definite article a:

em
- a → na
em
- o → no
em
- as → nas
em
- os → nos

So:

em a rua is grammatically resolved to na rua = in the street / on the street.

Using em a rua without contracting is considered incorrect in standard Portuguese. You almost always use the contraction.

Does na rua mean “in the street” or “on the street”? Which preposition would be closest in English?

Literally, na rua is “in the street”, but in English you’ll nearly always translate it as on the street, because that’s the natural English collocation.

So:

na rua → on the street (in normal everyday contexts)
na casa → in the house
na mesa → on the table (physically on top)

Portuguese uses em/na both for what English treats as in and on, depending on the noun. You have to pick the English preposition that sounds natural in context. For rua, that’s on: trash on the street.

Could I say Ontem vi muito lixo na rua instead? Is there a difference in meaning?

Yes, Ontem vi muito lixo na rua is perfectly correct and very natural.

The difference:

vi (I saw): neutral visual perception; you simply saw it.
reparei em (I noticed): you noticed it, paid special attention; maybe it struck you as unusual or noteworthy.

So Ontem reparei em muito lixo na rua subtly emphasizes that the trash caught your attention. Ontem vi muito lixo na rua is more matter‑of‑fact.

Is reparar em always “to notice”? Are there other verbs I could use here?

In the sense of “to notice”, reparar em is very common in European Portuguese. Alternatives include:

notar – to notice
- Ontem notei muito lixo na rua.
aperceber‑me de – to become aware of
- Ontem apercebi‑me de que havia muito lixo na rua.
perceber – often “to realize / understand”, but sometimes “to notice”
- Ontem percebi que havia muito lixo na rua.

However, reparar em is a very natural, everyday choice for visually noticing something, especially in Portugal:

Não reparei em ti na estação. – I didn’t notice/see you at the station.

If reparar can mean “to repair”, how do I know which meaning is intended in reparei em muito lixo na rua?

You distinguish the meanings by:

Structure
- reparar em X → “to notice X”
- reparar X (direct object, no em) → “to repair/fix X”
Context
- Ontem reparei em muito lixo na rua. – The only logical meaning is “noticed”, because you don’t “repair” trash.
- Ontem reparei a porta. – Here it clearly means “I repaired the door.”

So the presence of em (and the kind of object) makes the meaning unambiguous.

Would the sentence look or sound different in Brazilian Portuguese?

The sentence Ontem reparei em muito lixo na rua is perfectly understandable in Brazil, but there are some tendencies:

In Brazil, for “notice”, people use perceber, notar, or just ver more frequently in everyday speech; reparar em is less common in this sense.
- Ontem percebi muito lixo na rua.
- Ontem vi muito lixo na rua.
Pronunciation differs (EU vs BR accent), but the written form can be the same.

For European Portuguese learners, though, Ontem reparei em muito lixo na rua is very natural and idiomatic.