Hey Dom,

Long time no see. 作用 is some sort of function or effect:

動物試驗證實了這種新藥的抗癌作用 - Animal testing confirmed the anti-cancer effects of this new type of medicine (this medicine is effective in fighting against cancer)

過渡句的作用是承上啟下，使文章過渡自然 - the function of transitional sentences is to link what comes before to what comes after, and to make the transitions natural

雙語教學對外語學習的促進作用是不言而喻的 - The accelerating effects of bilingual teaching on the study of a second language are self-evident (speeds up the learning process)

他這種蚍蜉撼樹的舉動，對事情的發展，一點作用也沒有 - The small action he took had no effect on the development of the situation

起 means "start" or "begin". So 起作用 means "to cause an effect" or "to start having an effect"

在世界的進步中，起作用的不是我們的才能，而是我們如何運用才能 - In the improvement of the world, the thing that has an effect isn't our abilities, rather it's how we put them to use

家庭熏陶對孩子成長起很大的作用 - Family influence has a large effect on the raising of a child (i.e. how the child turns out)

老師的一番藥石之言對他也不起多大作用 - The teacher's advice didn't really have any effect on him

他在歷史上起了不可估量的作用 - He had an immeasurable impact on history

Hope that clears things up. Always worth checking a sentence bank like this one: <a href="https://zaojv.com/9708346.html" rel="noopener noreferrer" target="_blank">https://zaojv.com/9708346.html</a>;

Laurence

酵母在面包制作中起什么作用？起...作用=有...什么用途。

科技在抗击covid-19中起什么作用？起...作用=发挥了...长处。有...显而易见的不可替代的...。

As we can see, the character "起" is made of "走"(go) and "已"(already/off)。So “起作用” can be understood as "let the work/effect go/start" or "start off to work". If you know some German, it's quite useful to compare it with "los" and "ab".

起作用了=====It is working!!

起到xxxx作用 例如：对学生起到好的作用==对学生来说是好的

means It's good for students.