What other forms of the progressive verb can be shortened?


I see a lot of Japanese text shorten the progressive form by removing the い
from いる.

[code]

    戦っている  >  戦ってる
    
[/code]

I am wondering if it is ever acceptable to do so in other forms of the
progressive verb such as the masu form or past tense?

[code]

    戦っています  >  戦ってます?
    戦っていた  >  戦ってた?
    
[/code]




Generally, it can be shortened for very commonly used expressions coming after
the ~て form if they begin with another vowel (except u for various reasons,
unless someone wants to prove me wrong), it can be shortened. Thus the forms
you have written are acceptable, and possibly even more common in some
contexts. Here are some more situations in which this happens concerning the
~て form:

~てあげる > ~たげる, e.g. してあげる would become したげる.

~ておる > ~とる, e.g. しておる would become しとる (you wouldn't hear this in modern
standard Japanese; it happens in some dialects that still use おる rather than
いる, but other than that it sounds ridiculously silly in standard Japanese. You
might see it in anime and such, though.)

And of course, it is grammatical to use the polite ~ます forms in any of these
situations.




Generally, it can be shortened for very commonly used expressions coming after
the ~て form if they begin with another vowel (except u for various reasons,
unless someone wants to prove me wrong), it can be shortened. Thus the forms
you have written are acceptable, and possibly even more common in some
contexts. Here are some more situations in which this happens concerning the
~て form:

~てあげる > ~たげる, e.g. してあげる would become したげる.

~ておる > ~とる, e.g. しておる would become しとる (you wouldn't hear this in modern
standard Japanese; it happens in some dialects that still use おる rather than
いる, but other than that it sounds ridiculously silly in standard Japanese. You
might see it in anime and such, though.)

And of course, it is grammatical to use the polite ~ます forms in any of these
situations.

