Спасибо or благодарю – which one?

Both words for “thank you” are appropriate, and there is no particular context or region where one is used instead of the other. Having said that, there are some differences. Спасибо is one of the most commonly used Russian words, and you will hear it used much more often than the alternative. Благодарю is a more traditional Russian word for “thank you.” If you read Russian classical literature, this is the word you will encounter.

English has it too. These are called synonyms and every synonym always has at least a slight difference in meaning or usage. Благодарю is more formal and is rather similar to “I appreciate it”. Спасибо (вам/тебе) is equivalent to “thank you” and is more colloquial.

Спасибо comes from спаси Бог (God save), and благодарю from благо дарю (I give goodness). As already mentioned, the first one is more informal and common