The verb する is one of two key verbs in Japanese that are considered irregular, meaning they don't follow the conjugation rules for standard Godan and Ichidan verbs. The other is 来(く)る. する has a core meaning of 'to do' an action or 'to make' something happen.

• 掃除(そうじ)をする。
  To do the cleaning.
• 宿題(しゅくだい)をする。
  To do homework.

An action performed using する is usually marked with the particle を. In Japanese, する is classified as a さ-column irregular verb because when it is conjugated, the final る is dropped entirely rather than changing.

This leaves the initial す as the part that conjugates. As a result, する behaves partly like a る-Verb (by dropping る) and partly like an う-Verb (as the remaining す sound changes based on the conjugation). These changes can be seen in forms like the following.

（さ）せる, （し）ます, （す）る, （せ）よ.

We will cover each of these conjugations and what they mean in later lessons. For now, let's focus on the polite conjugation, します.

• 仕事(しごと)をします。
  To do work.
• 買(か)い物(もの)をします。
  To do the shopping.

Conceptually, する can be thought of as performing an action that has an observable result or effect on the world.