+1 for Libre Office (which is derived from Open Office).
My children have had Macs since they were small (two of three are now married!). We used to use Office for Mac, but it was simply too expensive.
Eldest still uses Libre Office on a PC (and is enthusiastic about it). Daughter #1's husband uses it on a PC laptop (she uses an iPad), Daughter #2 uses it on a Macbook Air, and I use it on Linux and even a version (Open Office) on my Android tablet. My other half is stubbornly sticking to a 15-year-old Mac, with MS Office Mac on it, but I've told her it'll be pensioned off very soon now! She's probably going to get Linux on cost grounds, but it'll be Libre Office, whatever hardware/OS she uses.
Libre Office is best described as 'Office of ten years ago' -- sensible menus, no "ribbons" or whatever other pointless junk -- and it opens and saves in the current MS file formats (and lots of others, such as PDF). Open Office is similar (they are very closely related), but in my experience Libre Office is more robust.
And, as Nev says, BOTH ARE COMPLETELY FREE.
E.