Why is Word Stress Important?
Word stress is not used in all languages. Some languages, Japanese or French for example, pronounce each syllable with eq-ual em-pha-sis.
Other languages, English for example, use word stress and pro-NOUNCE DIF-fer-ent SYL-la-bles with more or less im-POR-tance.
Word stress is not an optional extra that you can add to the English language if you want. It is part of the language! Fluent English speakers use word stress to communicate rapidly and accurately, even in difficult conditions. If, for example, you do not hear a word clearly, you can still understand the word because of the position of the stress.
Think again about the two words photograph and photographer. Now imagine that you are speaking to somebody by telephone over a very bad line. You cannot hear clearly. In fact, you hear only the first two syllables of one of these words, photo... Which word is it, photograph or photographer?
Of course, with word stress you will know immediately which word it is because in reality you will hear either...
So without hearing the whole word, you probably know what the word is...
It's magic! (Of course, you also have the context of your conversation to help you.)
This is a simple example of how word stress helps us understand spoken English–especially rapid spoken English. There are many, many other examples, because we use word stress all the time, without thinking about it.