Tu percebes quando estou cansado.

You realize when I am tired.

Breakdown of Tu percebes quando estou cansado.

• tu: you
• estar: to be
• cansado: tired
• quando: when
• perceber: to realise

Questions & Answers about Tu percebes quando estou cansado.

Why is tu used here, and how is it different from você in Portugal?

In European Portuguese, tu is the normal informal “you” for one person—used with friends, family, people your age, children, etc.

Você in Portugal is either avoided or sounds distant / a bit formal, and it actually takes third-person verb forms (like você percebe).

So in Portugal:

• Informal singular: tu percebes
• More distant / formal singular: você percebe (less common)
• Plural “you”: vocês percebem

Using tu here tells us the speaker is talking to someone they feel close or informal with.

Can I drop the tu and just say Percebes quando estou cansado?

Yes. Portuguese is a pro‑drop language: subject pronouns are often omitted because the verb ending already shows who the subject is.

So both are correct:

• Tu percebes quando estou cansado.
• Percebes quando estou cansado.

The second sounds very natural in conversation and is actually more common. Including tu can add emphasis or clarity (for example, contrasting with other people).

Why is there no eu before estou? Should it be quando eu estou cansado?

Both forms are correct:

• quando estou cansado
• quando eu estou cansado

Again, Portuguese usually drops pronouns when the verb ending clearly shows the subject. Estou can only be “I am”, so eu is not needed.

You add eu when you want extra emphasis or contrast, for example:

• Tu percebes quando eu estou cansado, mas ninguém mais percebe.
  (You notice when I am tired, but nobody else does.)

Why does the verb end in -es (percebes)? What’s the pattern?

Percebes is the present tense, second person singular of perceber (to understand/notice).

Present tense of perceber:

• eu percebo – I understand / notice
• tu percebes – you (singular, informal) understand / notice
• ele / ela / você percebe – he / she / you (formal) understands / notices
• nós percebemos – we understand / notice
• vocês / eles / elas percebem – you all / they understand / notice

So tu requires the -es ending in most regular -er verbs.

Does perceber mean “notice” or “understand”? Why use it here?

Perceber in European Portuguese commonly covers both:

• to understand (grasp mentally)
• to notice / realize / pick up on

In this sentence, Tu percebes quando estou cansado, it means something like:

• You notice / can tell when I’m tired.

In conversation in Portugal, people often use perceber where English might use “get,” “pick up on,” “realize.”

You could also hear:

• Tu notas quando estou cansado. (You notice when I’m tired.)
• Tu entendes quando estou cansado. (You understand when I’m tired.)

But perceber is very natural and common.

Could it also be Tu percebes que estou cansado? What’s the difference with quando?

Yes, Tu percebes que estou cansado is grammatically correct, but the meaning shifts slightly:

• Tu percebes quando estou cansado.
  You notice whenever / when I’m tired. (focus on the moment / situation)

• Tu percebes que estou cansado.
  You understand / realize that I’m tired. (focus on the fact / statement)

Quando introduces a time clause; que introduces a “that” clause explaining what you understand.

Why is it estou cansado and not sou cansado?

Portuguese uses:

• estar for temporary states or conditions (how you feel now)
• ser for permanent or defining characteristics

Tiredness is a temporary state, so you use estar:

• Estou cansado. – I’m tired (right now / at this time).

Sou cansado would sound like a permanent trait, almost “I’m a tired person by nature,” which is unusual and would need a special context.

Why is it cansado and not cansada? How does gender agreement work here?

Adjectives in Portuguese agree with the gender and number of the noun they describe. Here the implied subject is eu (I).

• If the speaker is male: (Eu) estou cansado.
• If the speaker is female: (Eu) estou cansada.

So the correct form depends on who is speaking, not on the person being addressed. The sentence as written assumes a male speaker.

Could the word order change, like Tu percebes quando cansado estou?

In modern Portuguese, the natural word order is Subject – Verb – (rest):

• (Tu) percebes quando estou cansado.

Putting estou after cansado (quando cansado estou) sounds old‑fashioned, poetic, or very marked. It’s not normal in everyday speech.

You can, however, move the quando clause:

• Quando estou cansado, tu percebes.

That’s correct and just adds a slightly different emphasis.

Is the tense after quando always the present indicative like quando estou?

When quando refers to real, habitual, or present-time situations, you normally use the present indicative:

• Tu percebes quando estou cansado.
  (Whenever I’m tired, you notice.)

For future events that are still uncertain or hypothetical, you often use the future subjunctive:

• Quando estiver cansado, vou para casa.
  (When I’m tired [in the future], I’ll go home.)

Here, the speaker is talking about a general, ongoing pattern, so quando estou (present indicative) is right.

How would this sentence change in Brazilian Portuguese?

In Brazil, tu is regional; você is much more common. Also, Brazilians use você with third-person verb forms:

Most typical in Brazil:

• Você percebe quando eu estou cansado.

Notes:

• Including eu is more common and natural in Brazilian Portuguese, though it can still be omitted: quando estou cansado.
• Pronunciation and intonation will also differ, but the structure is essentially the same.

Why don’t we need a preposition like de after perceber here?

Perceber can take:

• a direct object (no preposition):
  
  • Percebo o problema. – I understand the problem.
• or a clause introduced directly by que, quando, etc.:
  
  • Percebes que estou cansado.
  • Percebes quando estou cansado.

Because “when I’m tired” ( quando estou cansado ) is acting as the direct object of percebes, you don’t add a preposition like de.

Could this also mean “Do you understand when I am tired?” as a question?

Yes. Tu percebes quando estou cansado can be:

• a statement (with falling intonation):
  
  • You notice when I’m tired.
• a yes–no question (with rising intonation):
  
  • Do you notice / understand when I’m tired?

In writing, you’d mark the question with a question mark:

• Tu percebes quando estou cansado?