Word stress refers to emphasizing certain syllables within words for proper pronunciation in English. Most words have one syllable that is longer and louder than the others. The document outlines rules for determining stress patterns in different types of words like two-syllable words, compound words, words ending in certain suffixes, and prefixes. Mistakes in word stress can cause misunderstandings and prevent clear communication. Examples are provided to illustrate the rules. Exercises at the end test the reader's understanding of applying word stress rules.