why たい , たくない , ながら, etc arent considered verbal tenses?


If I'm right, all these forms modifies verbs , but when you look for them in
japanese verbal tenses you dont find them. Why do they treat them differently
to verbal tenses if japanese verbal tenses not only express time when an
action happens, but also other things such as command, desire, etc. Are there
more of these forms which arent listed as japanese verbal tenses?




The word ["tense"](https://en.wikipedia.org/wiki/Grammatical_tense) refers
specifically to grammatical time (past, future etc.) _-tai_ is not about time,
so it's not a tense.

But I think what you mean is verbal "conjugation" or "inflection": the various
forms a verb may take. Why isn't _-taku_ an inflection? Well, what counts as
"inflection" and what counts as a "verbal suffix" or "auxiliary" is kind of
arbitrary, and depends on the grammar. I don't know which grammar are you
using, so I don't know what are their criteria.

I'll use Japanese "school grammar" (the kind they teach to high-school kids)
as an example. In Japanese school grammar, a verb has five basic inflections
(活用形{かつようけい}), clearly visible by their different vowels in verbs like 書く:

  * 書か
  * 書き
  * 書く
  * 書け
  * 書こ

Why isn't _kakitai_ considered an inflection? Because they reserve the world
“inflection” (活用形) to mean those five basic forms, from which you can't escape
(you have to choose one of them every time you use a verb). Things like _-tai_
are called "verbal auxiliares" (or "auxiliary verbs"; 助動詞{じょどうし}), and each
auxiliary selects one of the inflections above; for example, _-tai_ wants the
_i_ -inflection ( _kak **i** -tai_), while _-nai_ prefers the _a_ -inflection
( _kak **a** -nai_). Here's one example of each:

  * **書か** -ない (not write)
  * **書き** -たい (want to write)
  * **書く** -べき (must write)
  * **書け** -ば (if write)
  * **書こ** -う (let's write)

Compared to inflections (活用形), auxiliaries (助動詞) are optional, and there's a
lot of them. For example, auxiliares using the _-i_ inflection, besides _-tai_
, include the following:

  * 書きたい "to want to write"
  * 書きます "to write" (polite)
  * 書きながら "while writing"
  * お書きする "to write" (humble)
  * お書きになる "to write" (honorific)
  * 書きけり "wrote!" (classical form)
  * 書きぬ "finished writing" (classical form)
  * …

Underlying all of them is the same basic 書き form; so it makes sense to have a
separate name ("inflection") for the basic forms, and another ("auxiliaries")
for the added-on plugins. The grammar you're using probably follows a similar
rationale.

(A note for completeness' sake: some of the added-on suffixes may have their
own inflections (書き **たい** 、書き **たかっ** た、書き **たく** ない；書か **ない** 、書か **なかっ**
た、書か **なく** もない, …). Others, like ば in 書けば or ながら in 書きながら, never change (that
is, they don't inflect). In school grammar, the latter are called 助詞{じょし}
(usually translated as "particles"). But these verbal 助詞 otherwise work just
like 助動詞, in that they're tacked on to the basic inflections.)




The word ["tense"](https://en.wikipedia.org/wiki/Grammatical_tense) refers
specifically to grammatical time (past, future etc.) _-tai_ is not about time,
so it's not a tense.

But I think what you mean is verbal "conjugation" or "inflection": the various
forms a verb may take. Why isn't _-taku_ an inflection? Well, what counts as
"inflection" and what counts as a "verbal suffix" or "auxiliary" is kind of
arbitrary, and depends on the grammar. I don't know which grammar are you
using, so I don't know what are their criteria.

I'll use Japanese "school grammar" (the kind they teach to high-school kids)
as an example. In Japanese school grammar, a verb has five basic inflections
(活用形{かつようけい}), clearly visible by their different vowels in verbs like 書く:

  * 書か
  * 書き
  * 書く
  * 書け
  * 書こ

Why isn't _kakitai_ considered an inflection? Because they reserve the world
“inflection” (活用形) to mean those five basic forms, from which you can't escape
(you have to choose one of them every time you use a verb). Things like _-tai_
are called "verbal auxiliares" (or "auxiliary verbs"; 助動詞{じょどうし}), and each
auxiliary selects one of the inflections above; for example, _-tai_ wants the
_i_ -inflection ( _kak **i** -tai_), while _-nai_ prefers the _a_ -inflection
( _kak **a** -nai_). Here's one example of each:

  * **書か** -ない (not write)
  * **書き** -たい (want to write)
  * **書く** -べき (must write)
  * **書け** -ば (if write)
  * **書こ** -う (let's write)

Compared to inflections (活用形), auxiliaries (助動詞) are optional, and there's a
lot of them. For example, auxiliares using the _-i_ inflection, besides _-tai_
, include the following:

  * 書きたい "to want to write"
  * 書きます "to write" (polite)
  * 書きながら "while writing"
  * お書きする "to write" (humble)
  * お書きになる "to write" (honorific)
  * 書きけり "wrote!" (classical form)
  * 書きぬ "finished writing" (classical form)
  * …

Underlying all of them is the same basic 書き form; so it makes sense to have a
separate name ("inflection") for the basic forms, and another ("auxiliaries")
for the added-on plugins. The grammar you're using probably follows a similar
rationale.

(A note for completeness' sake: some of the added-on suffixes may have their
own inflections (書き **たい** 、書き **たかっ** た、書き **たく** ない；書か **ない** 、書か **なかっ**
た、書か **なく** もない, …). Others, like ば in 書けば or ながら in 書きながら, never change (that
is, they don't inflect). In school grammar, the latter are called 助詞{じょし}
(usually translated as "particles"). But these verbal 助詞 otherwise work just
like 助動詞, in that they're tacked on to the basic inflections.)

