What does it mean to use a する verb without する?


> その絵はほとんど完成だ。

I find this sentence quite confusing. 完成 means the act of completion, so I
don't understand why だ is used instead of a variation of する. The meaning seems
different than a sentence like 今は勉強だ where it says that something is in the
process of the する verb rather than being in the state after the する verb as
implied in the above example.

Also, when a character says 了解 after receiving a command, are they omitting した
or です? It's very complex since there are times when a character will say
"これを召喚！" and it means "I will summon this" or "I summon this" and despite
following the format of omitting something, they mean different things.




> **Q. What does it mean to use a する verb without する?**

**A.** 完成 is a noun (meaning 'complete' or 'completion'). する is added to it to
make it a verb (meaning 'to complete'). For example "That picture is mostly
complete (in a state of completion)." (その絵はほとんど完成だ。）as opposed to "I've mostly
completed that picture." (その絵はほとんど完成しました。）

When you see 熟語{じゅくご} (compound characters, such as 完成、勉強、了解、召喚 etc.) followed
by する it is taking the noun form and making it a verb. As for looking for what
is being omitted, you can look at the context and particles surrounding the
熟語. For example, when someone says 了解, they could be saying two different
things with the basically the same meaning. 了解（しました）-I understood/got it/roger
that **or** 了解（です）-lit. (It) is understanding/comprehension (i.e., I
understand).

