@
cmdOptionKana 见到 dynamic 就盲猜只有形容词性就罢了，别人指出作为名词不同的义项还死不承认……
事实上一般语用中，“动力学”基本全用复数（除非是强调“一种”动力学，这种用法极少），反倒是“互动”单复数都在用的，还不算罕见。
引用自
https://en.wiktionary.org/wiki/dynamic：Noun
dynamic (plural dynamics)
A characteristic or manner of an interaction; a behavior. quotations ▲
Watch the dynamic between the husband and wife when they disagree.
2021 February 2, Katharine Murphy, The Guardian[1]:
One of the under-reported dynamics during the coronavirus pandemic has been the collapse of One Nation’s vote.
(physics) A moving force.
The study of fluid dynamics quantifies turbulent and laminar flows.
...
（从义项顺序可以看出点问题。）
词典的权威性暂且不论，这里 [1] 可是的现代的母语用户在正式场合的实例。如有不服，请联系原作者以便教育他们如何正确使用英语词汇。
所以这楼里到底是谁在闹笑话呢？
[1]
https://www.theguardian.com/australia-news/commentisfree/2021/feb/02/scott-morrison-must-heed-the-lesson-of-donald-trump-and-slap-down-craig-kelly