O vidro está limpo.

Because está is used for a state or condition, while é is used for a more essential or permanent characteristic.

In O vidro está limpo, clean is understood as a current condition: the glass is clean now.

• O vidro está limpo. = The glass is clean.
• O vidro é transparente. = The glass is transparent.

So here, estar + adjective means the glass is in a clean state.

Vidro literally means glass. Depending on context, it can refer to:

• the material itself: glass
• a glass pane: window glass
• sometimes, by context, the glass part of a window

So O vidro está limpo could mean:

• The glass is clean
• The windowpane is clean

If you specifically want window as the whole object, Portuguese usually uses janela.

• A janela está limpa. = The window is clean.

O is the definite article meaning the.

• o = the for a masculine singular noun
• vidro is a masculine singular noun

So:

• o vidro = the glass

Portuguese uses definite articles more often than English does, so including o here sounds very natural.

Because adjectives in Portuguese usually agree with the noun in gender and number.

Vidro is masculine singular, so the adjective must also be masculine singular:

• vidro limpo = clean glass

Here are the forms of limpo:

• limpo = masculine singular
• limpa = feminine singular
• limpos = masculine plural
• limpas = feminine plural

Examples:

• O vidro está limpo.
• A janela está limpa.
• Os vidros estão limpos.
• As janelas estão limpas.

The accent in está shows the stressed syllable and is part of the correct spelling.

• está = is
• stress falls on the second syllable: es-TÁ

This helps distinguish pronunciation and follows Portuguese spelling rules. In practice, you should just learn está as the standard 3rd-person singular form of estar in the present tense.

A natural Brazilian Portuguese pronunciation is approximately:

u VEE-dro es-TA LEEM-pu

A few notes:

• o often sounds like u when unstressed
• vidro sounds roughly like VEE-dro
• está has stress on the last syllable: es-TA
• limpo sounds roughly like LEEM-po, though the final o often sounds closer to u

This is only an approximation for English speakers, but it is a useful starting point.

The structure is:

article + noun + verb + adjective

So:

• O = the
• vidro = glass
• está = is
• limpo = clean

Portuguese word order here is very similar to English:

• O vidro está limpo.
• The glass is clean.

You usually would not say that in normal Portuguese.

O vidro está limpo sounds natural because Portuguese commonly uses the definite article before a specific noun.

Without the article, Vidro está limpo sounds unnatural in most everyday contexts.

Compare:

• O vidro está limpo. = The glass is clean.
• Um vidro está limpo. = A glass / one pane of glass is clean.

In this sentence, limpo is an adjective meaning clean.

It comes from the verb limpar (to clean), but here it is not functioning as a verb. It is describing the noun vidro.

So in O vidro está limpo, limpo means the glass is in a clean condition.

You make the noun, verb, article, and adjective agree in the plural:

• O vidro está limpo. = The glass is clean.
• Os vidros estão limpos. = The glasses / the panes are clean.

Changes:

• o → os
• vidro → vidros
• está → estão
• limpo → limpos

Yes, it can, depending on context.

Vidro can refer to glass as a material or a glass object, but if you specifically mean a drinking glass, Brazilian Portuguese more often uses:

• copo = drinking glass / cup

So:

• O copo está limpo. = The glass is clean.
• O vidro está limpo. = The glass / glass pane is clean.

If there is no context, many people may understand vidro as glass material or window glass, not necessarily a drinking glass.

In Brazilian Portuguese, you can often make a statement into a question just by using rising intonation:

• O vidro está limpo? = Is the glass clean?

The word order usually stays the same. Portuguese does not normally need do/does/is inversion the way English does.

You make it negative by putting não before the verb:

• O vidro não está limpo. = The glass is not clean.

This is the standard way to negate a sentence in Portuguese:

• não + verb

Yes. Sujo means dirty, and it follows the same pattern:

• O vidro está sujo. = The glass is dirty.

This is a very useful contrast pair:

• limpo = clean
• sujo = dirty

Both adjectives agree with the noun just like limpo does.