1. What is an adjective?
 
　　An adjective indicates a quality or state of the person or thing referred to by a noun, as in English, e.g.
 
　　 红(red)　 高(high) 　大(big)　 冷(cold) 　好(good)　 迅速(quick)　 匆忙(busy)
　　 美丽(beautiful) 　愉快(happy)　 安静(quiet)　 光明(bright) 　绿油油(green and sleek)
 
　　Onomatopoeias imitating a sound are also classified into this category, e.g.
 
　　 砰(thump)； 叮当(jingle)； 咕咕(coo, of a dove or pigeon) 
 
2. What is noteworthy about Chinese adjectives 
 
2.1. The reduplicated forms of adjectives: “AA”, “AABB”, “A不A”, etc. 
 
　　Most of Chinese adjectives may be reduplicated to be more effective in description or used in “A不A”,”AB不AB” alternative question forms, e.g.
 
　　红红的山茶花 (very, very red camellia) --- AA
　　静静的海洋 (very, very calm sea) --- AA
　　好好儿想一想 (give it careful thought) --- AA + 儿
　　平平安安过日子 (live in quiet and peace) --- AABB
　　欢欢喜喜迎新年 (celebrate a happy New Year) --- AABB
　　好不好？(Is it good or not?) --- A不A
　　我够不够高？(Am I tall enough?) --- A不A
　　这电影好看不好看？(Is it an interesting film?) --- AB不AB
　　这姑娘可爱不可爱？(Is she a pretty girl?) --- AB不AB 
 
2.2. No changes in comparison 
 
　　A Chinese adjective does never change its form when being used in comparison, e.g.
 
　　老王比老张更年轻。(Lao Wang is younger than Lao Zhang)
　　老李在我们当中最年轻。(Lao Li is the youngest among us)
 
　　As examples above, we add a word (“更” or ”最”) before each “年轻” respectively to show its degree. But in many cases degree word is not essential in use. For example, we can simply say老王比老张年轻, because the phrase “比老张” already tells us that “年轻” is a result of comparison.