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

Yes

The word "marco" maintains the same meaning, spelling, and grammatical function in both Brazilian and Continental Portuguese. It can refer to a physical marker (like a stone post), a historical milestone, a landmark, or a regulatory framework (marco regulatório). The only difference is in pronunciation. In Brazilian Portuguese, the unstressed final "o" is typically pronounced as a mid-back rounded vowel [o]. In Continental Portuguese, unstressed final vowels are often reduced, meaning the "o" in "marco" sounds much closer to [u] (as in "boot").

Brazilian Portuguese Examples

1. Esse projeto é um marco para a nossa empresa. (This project is a milestone for our company.)
2. O novo marco regulatório mudou o setor. (The new regulatory framework changed the sector.)
3. A descoberta foi um marco para a ciência. (The discovery was a milestone for science.)
4. O monumento serve como um marco histórico. (The monument serves as a historical landmark.)
5. Colocaram um marco de pedra para dividir os terrenos. (They placed a stone marker to divide the lands.)

Continental Portuguese Examples

1. Este projeto constitui um marco para a nossa empresa. (This project constitutes a milestone for our company.)
2. O novo marco regulatório alterou o setor. (The new regulatory framework altered the sector.)
3. A descoberta foi um marco para a ciência. (The discovery was a milestone for science.)
4. O monumento serve como um marco histórico. (The monument serves as a historical landmark.)
5. Colocaram um marco de pedra para delimitar os terrenos. (They placed a stone marker to delimit the lands.)