Here are a few of the most common conjunctions you'll come across in Spanish.
Common Spanish Conjunctions
Pero, Sino, and Mas
These three conjunctions can all be translated as but, but they're not interchangeable.
Pero and Mas
Pero and mas mean but and are used to contrast two statements. However, mas is considered to be more literary, and is something you're much more likely to see in formal writing.
Sino also means but, but is used to introduce an affirmation that contrasts a previous negative statement.
Y and E
When y comes before a word that begins with a i- or hi-, it changes to an e.
Y does not change to e before words that begin with hie-.
O and U
When o comes before a word that begins with a o- or ho-, it changes to an u.