Why similar languages can sound differentlly

Spanish and Portuguese are so similar. But they sound very differently.

The channel introduced here is Airlearn. Apart from being a language channel, it is also an emerging language learning platform.

The lexical similarity between Spanish and Portuguese attains 89%, which is more than that between Catalan and Spanish (85%). This implies that Spanish speakers are able to read Portuguese without problems, but understanding spoken Portuguese tells a different story. To the untrained ear, European Portuguese might sound like Russian.

Unlike a syllable timed language as Spanish, European Portuguese is stress timed. Thereby stressed syllables are pronounced at constant pace, while in non-stressed syllables the vowels are omitted, shortened or adapted. The final -a is morphed to a schwa. The final -o is morphed to an -u and the final -e to a short -i. Initial vowels are often dropped. Both in Spanish and Portuguese 'esperado' is the past participle 'waited'. In European Portuguese, the leading 'e' is dropped, the second one muted to schwa, the stressed 'a' is unchanged and the final -o is muted to -u. Moreover the now leading -s is pronounced -sh.

Diphtongation and nasalation are two more distinct features separating Portuguese from Spanish. Both are left-overs of the Ibero-Celtic languages that were spoken in Portugal before the Roman invasion. 

The common termination -ción becomes a nasalized -ção. This is typical for Portuguese. 

Despite keeping the Latin -tion for these words, nasalization also occurs in French and English but it takes a different turn. 

Furthermore, some consonants are often dropped, while others are flipped. Most often those are 'l' to 'r', 'p' to 'b' and 'b' to 'v'. The double 'rr' has initially been pronounced 'R' like in French, while it now has shifted further to an atypical guttural fricative. In Portuguese the -s between vowels is pronounced 'z' which then requires doubling it to keep the 's' pronunciation.

Examples: 'blanco' becomes 'branco', 'patata' becomes 'batata'. 'Libro' becomes 'livro' and 'libre' becomes 'livre'. However 'Libertad' keeps the -b, but gets a muted -e appended: 'Libertade'.