The word "征兆" is formed through the semantic combination of two characters, "征" and "兆", each carrying related meanings of "sign" or "omen". By joining these synonymous elements, the compound reinforces and intensifies the concept, resulting in a term that specifically denotes a perceptible indication or precursor, often of something imminent or significant. This process exemplifies how Chinese often creates words by pairing characters with overlapping meanings to convey a unified, nuanced idea.