Complex sentence: That is, if the last syllable of a word is short, then the penultimate syllable will be stressed, while if the last syllable contains either a long vowel or a diphthong, then it receives primary stress.
Split into simpler sentences: That is, if the last syllable of a word is short, then the penultimate syllable will be stressed. If the last syllable consists of either a long vowel or a diphthong, the last syllable receives primary stress.