Stress is emphasis given to certain syllables in words. In English, stress is produced with a longer, louder and higher pitched sound than unstressed sounds.
The word 'banana' has stress on the second syllable, the word 'photographic' on the third.
In the classroom
Unlike many languages, stress in English is unpredictable, and learners generally need to memorise individual words. Areas for teachers to focus on include word families, which show different stress patterns, e.g. 'photo', 'photographer', and 'photographic', and some words that have different stress in different forms, e.g. 'produce' and 'desert', verb and noun.