My last post on free software I use mentioned a substitute for using search engines for word definitions.
Another common use of search engines is unit conversions (e.g. 3 miles to km). For that and more, I use GNU units (https://www.gnu.org/software/units/).
I can't do any justice to this program with the number of characters I have left, so please, check it out; you won't be disappointed.
Mike Gerwitz's personal Mastodon instance