Is the word fronteira the same in Brazilian and European Portuguese?

Yes

The word "fronteira" has the same meaning, spelling, and grammatical function in both Brazilian and Continental Portuguese. The primary difference lies in pronunciation.

In Brazilian Portuguese, vowels are generally more "open" and clearly articulated. In Continental Portuguese, the language is more "stress-timed," which leads to significant vowel reduction. This means that unstressed vowels (like the "e" in fronteira) are often pronounced more closed, or even almost swallowed, making the word sound more clipped to a Brazilian ear.

Brazilian Portuguese Examples

1. Estamos cruzando a fronteira agora. (We are crossing the border now.)
2. A fronteira entre o Brasil e o Paraguai é muito movimentada. (The border between Brazil and Paraguay is very busy.)
3. Tem muita polícia na fronteira hoje. (There is a lot of police at the border today.)
4. Eles estão patrulhando a fronteira para evitar o contrabando. (They are patrolling the border to prevent smuggling.)
5. A fronteira entre a razão e a emoção é tênue. (The border between reason and emotion is thin.)

Continental Portuguese Examples

1. Estamos a cruzar a fronteira agora. (We are crossing the border now.)
2. A fronteira entre Portugal e Espanha é extensa. (The border between Portugal and Spain is extensive.)
3. Há muita polícia na fronteira hoje. (There is a lot of police at the border today.)
4. Eles estão a patrulhar a fronteira para evitar o contrabando. (They are patrolling the border to prevent smuggling.)
5. A fronteira entre a razão e a emoção é ténue. (The border between reason and emotion is thin.)