Stress word in English helps you to pronounce the words correctly. Although, stressing a wrong syllable in speech does not make your speech incomprehensible, it makes your English sound somehow primitive.
The most difficult part for learners of English is to identify the stressed syllables. Since the best way of learning English is copying from native speakers of English (like most of the learners of English copy the pronunciation of native speakers of English), then copying the word stress native speakers of English use in speech seems to be the best way of identifying and learning the word stress.
In order to identify the stressed syllables we have to understand what the speaker does in producing them and what makes that sound to be seen as stressed for the listener.
From the point of view of the speaker things seem to be simple. A syllable is believed to be stressed if the speaker uses more muscular energy in producing it than it is used when producing an unstressed syllable. When the speaker produces stressed syllables, he produces higher glottal pressure because the muscles used to expel air from the lungs are more active.
When it comes to the perception of stress by the listener things are completely different. Many different characteristics of sound make a syllable recognizably stressed. However, one common characteristic is found in all stressed syllables. This common characteristic is known as the prominence of the syllable (Note: “Prominence” is what sets a thing apart from others).
There are four different things that allow us to recognize a syllable as being prominent, so we can recognize it as stressed:
We can conclude that the prominence of a syllable is affected by four factors: loudness, length, pitch, and quality. Usually these four factors work together in creating stressed syllables but many times just one or two of these can make a syllable prominent, perceived as stressed. Pitch and length is proven to be more effective than loudness and quality and this is something good to keep in mind.