Is た form included in dictionary 辞書 form?


I know the dictionary form ends with う、す、る、etc. But what about the changed
forms of them such as 買った、食べなかった? Can I also call these dictionary form?




_Dictionary form_ is exactly that: it is the form by which you can look up a
word in a dictionary.

It you take a verb like 買う you can _inflect_ it to get other forms such as
買わない or 買わなかった or 買った. But, try as you might, you will not be able to look up
these forms in a standard dictionary. You need to be able to recognize that
they all derive from the _dictionary_ form.

Typically, for someone learning Japanese, you should note that these _forms_
are all _informal_ forms. Their _formal_ counterparts being 買いません, 買いませんでした,
and 買いました respectively.

Generally, the _informal_ forms are found embedded in a sentence. For example,

> 本を買った人があそこにいます。

> The guy who bought the book is over there.

The _dictionary_ form is often the starting point from which you derive all
else.

If you want a name for the other forms, I would suggest calling them either
_derived_ or _inflected_ forms. Most people proficient in Japanese will
understand what you're referring to.

**Edit**

I would say that _plain_ and _dictionary_ forms generally refer to the same
thing. I would say that _casual_ and _informal_ also refer to the same thing.
But while all _plain_ forms are also _informal_ , the same is not true the
other way.

If you need a catch-all to describe the verb forms you are talking about, I
would say something like "the dictionary form and its other inflected informal
forms". That's a bit of a mouthful. But, I'm not sure that you would need to
talk about these all together very much (unless you intend to become a
_grammatologist_ --did I just make up a word?).

