Learn Hardcore Portuguese (Portugal): À noite, a lua reflete‑se na água do lago. - At night, the moon is reflected in the lake’s water.

À noite = at night (as a general time of day)
- Example: À noite, estudo português. – At night, I study Portuguese.
A noite (without accent) usually means the night as a noun, referring to a specific night or the nighttime in general as a thing.
- Example: A noite estava fria. – The night was cold.
Na noite = em + a noite → in the night / on that night (more specific, often one particular night).
- Example: Na noite de sábado, saí com amigos. – On Saturday night, I went out with friends.

So in your sentence, À noite sets the time in a general sense: At night, the moon reflects on the water of the lake.

Why does À noite have a grave accent (à)? What is that accent showing?

The grave accent in à shows a contraction of two identical vowels: the preposition a + the feminine definite article a.

a (preposition) = to, at
a (article) = the (feminine)

So:

a + a noite → à noite (to/at the night → at night)

This type of contraction with a + a is called crase in Portuguese. You see it often in time expressions:

à tarde – in the afternoon
à noite – at night
à segunda‑feira – on Monday

Why is there a comma after À noite?

À noite is an adverbial phrase of time placed at the beginning of the sentence. In Portuguese, when such a phrase comes first, it is very common (though not always absolutely mandatory) to separate it with a comma.

À noite, a lua reflete‑se na água do lago.
= At night, the moon reflects on the water of the lake.

If you moved the time phrase to the end, you would normally drop the comma:

A lua reflete‑se na água do lago à noite.

Why do we say a lua instead of just lua? Do we always use the article with lua?

In European Portuguese, definite articles are used much more often than in English, especially with:

natural elements (the sun, the moon, the sea, the sky)
general nouns you might leave bare in English

So:

a lua = the moon
o sol = the sun
o mar = the sea

You will normally say a lua when talking about the moon in general. Dropping the article (lua reflete‑se…) would sound unnatural in this sentence in European Portuguese.

In some fixed expressions or poetic language, the article might be omitted, but the everyday, neutral way is a lua.

What is the function of ‑se in reflete‑se? Why is the verb reflexive here?

The ‑se is a reflexive / pronominal clitic pronoun. In this sentence, refletir‑se is used in a pronominal sense to express that the image of the subject appears reflected.

a lua reflete literally = the moon reflects (something)
a lua reflete‑se = the moon is reflected / reflects itself (in something)

Portuguese often uses reflexive/pronominal verbs where English uses a simple active or passive construction:

O sol reflete‑se na água. – The sun is reflected in the water.
O prédio vê‑se daqui. – The building can be seen from here.

So reflete‑se here means is reflected, not that the moon is doing something to itself in a conscious way.

Why is it reflete‑se (pronoun after the verb) and not se reflete?

In European Portuguese, the default position of unstressed pronouns (like se) in a simple affirmative main clause is after the verb, attached with a hyphen. This is called enclisis.

A lua reflete‑se… ✅ (standard EU Portuguese)

You move the pronoun before the verb (proclisis) mainly after certain words, such as:

negation: não, nunca
some adverbs: já, ainda, sempre
certain conjunctions and pronouns: que, quem, quando, etc.

Examples:

A lua não se reflete na água.
Quando a lua se reflete na água, parece maior.

In Brazilian Portuguese, se reflete is much more common even in simple affirmative sentences, but in European Portuguese, reflete‑se is the neutral pattern in this context.

Could we say A lua reflete na água do lago without ‑se? Is that wrong?

You could hear refletir without se, but:

A lua reflete‑se na água do lago.
is the natural, standard way to talk about its image appearing on the water.

Saying A lua reflete na água do lago is grammatically possible, but it sounds less idiomatic and may suggest that the moon is reflecting something onto the water (e.g. light) rather than that its image appears there.

So for the idea of its reflection appearing on the water, reflete‑se is strongly preferred.

What does na in na água mean? How is it formed?

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

em + a = na
- em = in, on, at
- a = the (feminine)

So:

na água = in the water / on the water

Similarly:

no lago = em + o → in the lake
nas árvores = em + as → in/on the trees

What does do in do lago mean? How is it different from de lago?

Do is a contraction of de + o:

de + o = do
- de = of / from
- o = the (masculine singular)

So:

do lago = of the lake → the water of the lake

Using de lago (without the article) would normally mean of a lake / lake‑ (in a more generic or descriptive sense) and is much less common here. We are talking about a specific lake, so do lago is appropriate.

What are the genders of noite, lua, água, and lago, and how can I see that in the sentence?

You can see the grammatical gender from their articles:

a noite → feminine (article a)
a lua → feminine
a água → feminine
o lago → masculine

In the contractions:

à noite = a (prep.) + a noite (feminine)
na água = em + a água (feminine)
do lago = de + o lago (masculine)

Often nouns ending in ‑a are feminine and ‑o masculine, but there are many exceptions, so the article is your most reliable guide.

How do you pronounce reflete‑se in European Portuguese?

In European Portuguese, reflete‑se is roughly:

IPA: [ʁɨˈflɛ.tɨ.sɨ] (approximate)

Broken down:

re‑ → like a very short rɨ; the r is a guttural sound (in the throat)
fle‑ → flé with an open e (like e in bed)
te → weak tɨ (the final e is very reduced)
‑se → sɨ (a weak vowel, not like full English see)

Stress is on fle: re‑FLE‑te‑se.

Note: In careful speech you hear the small vowel in ‑se; in fast speech it can be very reduced.

Is the word order fixed, or could we move parts around, like À noite, na água do lago, a lua reflete‑se?

Portuguese word order is more flexible than English, especially for adverbial phrases. All of these are grammatically possible, with slightly different emphasis:

À noite, a lua reflete‑se na água do lago.
(time first – neutral and natural)
À noite, na água do lago, a lua reflete‑se.
(more literary/emphatic; highlighting both at night and on the lake’s water)
A lua reflete‑se na água do lago à noite.
(time at the end, still very natural)

The most neutral everyday version is the original one.

Why is lua not capitalised, while in English we often write the Moon with a capital M?

Portuguese usually treats lua, sol, terra (moon, sun, earth) as common nouns, so they are written with lowercase letters in normal text:

a lua – the moon
o sol – the sun
a terra – the earth / the ground

They may be capitalised in certain astronomical or very formal contexts, but in ordinary writing, lowercase is standard. English is more likely to treat Moon, Sun, Earth as proper names and capitalise them.