/etc/fstab entries missing "defaults" option, is it implicit?

My automatically generated /etc/fstab file has most of it's entries like so # /dev/sda9 UUID=8de1f4d1-4620-49f0-aeaf-a499f7cb6c21 /home ext4 rw,relatime 0 2 It's missing the defaults option. My system works fine, but I am not sure if: 1) Default values are implicitly set, if so, why is rw there? I can't see any notice that they are implicit in the man page. 2) My system is mis-configured and just happens to be running ok (for months) and I should insert the defaults option (maybe for async, etc). My system is Arch with Systemd, maybe that is picking up the slack.