Obligatory note that /etc/profile and ~/.profile are only run by login shells, and many terminal emulators do not execute a login shell by default.

Unfortunately, there is no standard secondary place* that all shells execute, so check your chosen shell’s manual for what it does run on startup and put your functions into one of those. Preferably one that goes in your homedir.

Alternatively have that file source ~/.profile assuming that won’t cause an infinite loop.

* And not even a primary if you count *csh, but if you use those you have other problems.