They are all vocabulary from HSK 4. They are all verbs, and they are translated as “adapt”, “fit”, “suit”. Is there any difference in use or meaning between them? Thank you so much!
符合 means "match". Example:
他 符合 我们的 要求。
He matches our requirement.
适合 means “fit” in a sense of "good fit". Example:
他 很 适合 这个 职位。
He is a good fit.
符合 and 适合 have similar meanings but are often paired with different nones. I would say 符合 is a more precise fit than 适合。
适应 mean something quite different. It means "get used to", it is the process of getting to 符合 and 适合.
符合 is a transitive verb and means "to meet (a requirement)"， “to comply with". It's used mostly when talking about the accordance of something with some rule, form or standard.
出口产品必须符合相关法律法规 export products must comply with the relevant rules and regulations
你的思维不太符合逻辑 your line of thought isn't very logical (compliant with logic)
适合 is a transitive verb and means "to suit (someone/something)", or "to be suitable"; as opposed to 合适 which is always an adjective. It can also be used as "appropriate" (still transitive).
这很适合我的口味 this really suits my taste
适合野生动物栖息的地方 places that are suitable for wild animals (to dwell in)
跟朋友一起吃饭的时候不适合讨论政治问题 it's not appropriate to discuss politics when having dinner with friends
适应 can be used intransitively and transitively, and means "to adapt". Translating as "to fit/suit" is acceptable depending on the context, but the core meaning of the term is to adapt/adjust to something.
香港的气候我不适应 I can't adapt to the climate of Hong Kong
你可以更改这些字段的大小，以适应你的内容 you can change the size of these fields to fit (accommodate) your content
The book HSK汉语水平考试精选词汇辨析与练习 describes differences between closely related HSK words. Item 120 (page 119) addresses 符合, 合适, 适合, and 适应:
- 符合 合适 适合 适应
【符合】fú hé [accord with; tally with; conform to; coincide]
【合适】hé shì [fit; suitable; appropriate]
【适合】shì hé [agree with; suit; fit]
【适应】shì yìng [adapt; accommodate]
This last part explains their differences, which I translate to:
Both 合适 and 适合 indicate that actual situation is the same as the objective requirements, without contradiction; they can be modified by a degree adverb. The differences are that 合适 is an adjective, and is often used as a predicate [谓语], and also attribute (modifier) [定语], complement [补语], etc, cannot be used as an adverbial [状语]. 适合 is a verb. When used as a predicate [谓语] it can take an object [宾语] and can be used as an adverbial [状语]; it cannot reduplicate [重叠]; it is often used in written language. 符合 emphasizes that one thing is consistent with another, in some way such as quantity, shape, without discrepancy. 适应 emphasizes making appropriate changes or adjustments to suit objective conditions; in sentences it is more often a predicate [谓语], it can take an object [宾语]; can reduplicate [重叠] such as 适应适应.
I feel the biggest difference is that 合适 does not take an object, whereas 适合 can.
No object: 要是它不合适，你总还可以把它退回去嘛。 (YouDao)
If it doesn't suit, you always can return it.
Object: 这个太贵，而且颜色也不适合你。 (YouDao)
It's too expensive, and the color doesn't suit you.
My experience is that 符合 is typically used in formal settings (where there's some pre-defined specifications, like job applications), e.g.:
The light is designed in accordance with the new safety standards.
As the book above highlights, 适应 highlights a change to make something suitable.
I need to adapt to the new timetable.
I suggest taking a look at the above book which contains many examples, and even exercises.