不能说initiator是initial 的派生词。其实initiator和 initial 都是动词 initiate（创始，发起）的派生词。

initiate 例句：

The company initiated a management training programme for small businesses. 该公司发起了一项针对小企业经营管理的培训计划。

We shall initiate urgent discussions with our European partners. 我们将与欧洲伙伴展开紧急磋商。

initiator例句：

the initiator of the proposal 该项提议的发起人

one of the major initiators of the tumultuous changes in Eastern Europe 东欧剧变主要的发起者之一

initial例句：

My initial reaction was to panic. 我的第一反应就是惊慌。

Her initial [=first] reaction was to say no, but she eventually agreed to help. 她的第一反应是拒绝，但最终还是同意帮忙了。

At the initial stage of the project not everyone had access to a computer. 在这个项目的初始阶段，并非人人都能接触到计算机。

另补充：initiative

Mr Hills showed initiative and bravery when dealing with a dangerous situation. 希尔斯先生在应对险情时表现出了他的决断能力和英勇。

Employees are encouraged to use their initiative if faced with a problem. 公司鼓励雇员遇到问题时发挥主动性。