can i use bathroom fan in kitchen

[clarelouise]

hi can i use a bathroom fan in my kitchen by fixing filter in are over the fan some how
as the hole in wall is 100 mm
kitchen fans are a lot bigger

[buildersmate]

There is nothing to prevent you doing it, but it won't be as effective.
It is all about the volume of air moved by the fan blades per hour - kitchen fans move a lot more air to try and get rid of condensation from cooking over the hob - which is why they are more typically a special shape to fit over a hob.
Most kitchen fans take the hot steamy air from over the cooker and constrict it down to 100mm diameter hole in the wall - so size of hole isn't an issue.
Although kitchen fans have some sort of filter system and remove dirt and cooking fat, that a niceity - you don't have to have such a filter such the air is going outside anyway - just means the fan blades will need cleaning more often.
However in view of the hassle of doing this and the relative modest cost of a pukka kitchen fan, I wonder if this is really worth the trouble.