English is a stress-timed language

In English some words sound different when they are said on their own than they do when they are said as part of a sentence. That is why English is a stress-timed language. That means some syllables will be longer, and some will be shorter according to their importance in the sentence. The unstressed words are called "function words" and, on the other hand, the most important words of the sentence, which provide more information, are called "content words" In contrast, Spanish is a syllable-timed language, which means each syllable has the same length.