Learn Portuguese (Portugal): Esta é a quarta vez que ele falha.

Ordinal numbers (first, second, third, etc.) act like adjectives in Portuguese, meaning they must agree in gender and number with the noun they describe. Because vez (time/instance) is a feminine singular noun, the masculine quarto changes to the feminine quarta.

Do ordinal numbers always go before the noun, like in quarta vez?

Yes! While most regular descriptive adjectives in Portuguese usually come after the noun, ordinal numbers almost always come before the noun, just like they do in English.

Why does the sentence use vez for "time" instead of tempo?

Portuguese has two different words for "time". Vez is used when you can count the instances or occurrences (like this time, next time, the fourth time). Tempo is used for time as a general concept, duration, or the weather.

Why start with Esta rather than Este or Isto?

The word Esta (This) is a demonstrative pronoun that must agree with the noun it refers to. It points directly to a vez, which is feminine. You would use Este for a masculine noun, and Isto when referring to an abstract idea, a situation, or something completely unidentified.