All I can say is WOW… Just lots of different syntax. MOST of the commands are 3 letters for the verb, 3 letters for the noun, any options are in parenthesis, and special keywords are prepended by an asterisk (splat in as/400 land)

verbs include:
wrk = work
crt = create
del = delete
rmv = remove
dsp = display
chg = change

Nouns include:
job = job (a process)
obj = object (anything that can be created and deleted)
prf = user profile
val = value
rsc = resource

Pre-noun modifier:
dft = default
usr = user
act = active
sys = system
hdw = hardware
dup = duplicate

post-noun modifier:
d = description
L = List
E = Entry
Q = queue
F = file

All OS/400 standard (default) system objects, etc start with Q.
Often, users are created for certain types of jobs.

so the library QSYS is basically the system directory
QHST is the system history message queue

The problem is that not ALL things follow this convention, like WS is workstation.
Not all combos work, or some nouns only work with certain modifiers.

it’s all case insensitive.
there’s lots more than this.

Command examples:

DSPSYSVAL QTIME
this shows the system timestamp

ADDLIBLE
Add a library list entry (aka, add on to the end of the path for the current job)

CHGDFTLIB
Change the default library (current directory)

CPYF
copy a file

crtdupobj
create duplicate object (copy any object, not just a file)