For literal thickness:
* 厚 (hòu): Thick, heavy, substantial
* 薄 (báo): Thin, light, weak
For metaphorical "thick and thin" meaning:
* 厚薄 (hòu bó): Literally means "thick and thin," but often implies different levels of understanding, closeness, or experience.
* 深浅 (shēn qiǎn): Literally means "deep and shallow," often used metaphorically to express different levels of understanding, knowledge, or commitment.
* 浓淡 (nóng dàn): Literally means "concentrated and diluted," often used metaphorically to describe different intensities of emotion, flavor, or other qualities.
Specific examples:
* 经历过风雨 (jīnglì guò fēngyǔ): This literally means "experienced wind and rain," which is a common Chinese idiom for "going through thick and thin" together.
* 同舟共济 (tóng zhōu gòng jì): This literally means "sharing a boat and crossing a river together," implying mutual support and facing challenges as one.
The best choice for "thick and thin" in Chinese depends on the specific context and the nuance you want to convey. Choose the kanji that best fits the meaning you want to express.