This is the 2856th most frequent Polish word.
krótkim
"Short" (in instrumental or locative case form).
'Krótkim' is an adjective in the instrumental case, describing 'fasonie' (style) to specify the type.
Ma na sobie płaszcz w krótkim fasonie.
She is wearing a coat in a short style.
'Krótkim' is an adjective in the locative case, describing 'czasie' (time) to indicate the duration of time.
W krótkim czasie nauczył się obsługiwać komputer.
In a short time, he learned how to use the computer.
'Krótkim' is used as an adjective in the instrumental case to describe the manner in an abstract context, here 'sposób' (way).