In Debian useradd and userdel are low level utilities and their man pages recommend that administrators use adduser and deluser.

I've found a way to differentiate between the low level utilities and the recommended ones.

The low level utilities use "Latin" order where the verb component comes after the object and the recommended commands the other way around.

So the recommended commands' syllables' order matches that of our everyday language while the low level utilities' syllables' order matches that of a "dead" language.