Unix-like operating systems (Windows, too) use the concept of a PATH to search for binaries (or executables, in the case of Windows). The PATH is nothing more than a list of folders separated by the colon character ':' that tells the operating system where to look for binaries.

To add something to your PATH (and make it a permanent change), you need to edit either the .bash_profile (macOS) or .bashrc (Linux) files; these are located in the root folder for your user. Thus, to add both Scala and Maven binaries to the PATH, you can do the following (on macOS):

cp ~/.bash_profile ~/.bash_profile_old   # make a copy just in case

echo export SCALA_HOME=/opt/scala >> ~/.bash_profile

echo export MAVEN_HOME=/opt/apache-maven >> ~/.bash_profile

echo PATH=$SCALA_HOME/bin:$MAVEN_HOME/bin:$PATH >> ~/.bash_profile

On Linux, the equivalent looks as follows:

cp ~/.bashrc ~/.bashrc_old   # make a copy just in case

echo export SCALA_HOME=/opt/scala >> ~/.bashrc

echo export MAVEN_HOME=/opt/apache-maven >> ~/.bashrc

echo PATH=$SCALA_HOME/bin:$MAVEN_HOME/bin:$PATH >> ~/.bashrc

The preceding commands simply append to the end of either of the .bash_profile or .bashrc files using the redirection operator >>.

Once you execute the preceding commands, restart your Terminal, and:

echo $PATH

It should now include paths to both the Scala and Maven binaries.