The term ‘onomatopoeia’ refers to words whose very sound is very close to the sound they are meant to depict. In other words, it refers to sound words whose pronunciation to the actual sound they represent.
Words such as grunt, huff, buzz and snap are words whose pronunciation sounds very similar to the actual sounds these words represent. In literature such words are useful in creating a stronger mental image. For instance, sentences such as “the whispering of the forest trees” or “the hum of a thousand bees” or “the click of the door in the nighttime” create vivid mental images.