This is the 534th most frequent Chinese word.
子
"子" (zǐ) means "child," "son," or a suffix denoting a noun.
In this sentence, '子' is used as a bound morpheme in the word '椅子' (chair). It forms part of the noun but does not stand alone.
这个椅子的颜色很好看。
The color of this chair looks good.
Here, '子' is used in '粒子' (particle), where it indicates a smaller or individual unit of something.
空气中充满了微粒子。
The air is full of fine particles.
In this case, '子' is found in '孩子' (child or children), where it functions similarly to a suffix that modifies the word.