Please, how to find text left from dot?

Please, if I have expression like:

abc.def.gihj

How can I find text left form dot and right from dot?

I th think I have to COMbINE functions?

Please, is there any tutorial to reccomand?

Sth like:
=left (“aaaa.bbb.cccc”, search("."; “aaaa.bbb.ccc”))
???
Many thanks!