troff/nroff, motion

vertical motion

\v'N'
moves down. The default scaling factor is vs.
\v'-N'
Negative offsets move up.
\v'|N'
To move to an absolute position N, move relative by the distance from here to N.
\r
moves up one em in troff, one v in nroff.
\u text \d
moves up half a v, then prints text, then moves down half a v again. (It works the other way 'round, to.)

horizontal motion

\h'N'
moves horizontally. The default scaling factor is ems.
\h'-N'
Negative offsets move to the left.
\h'|N'
To move to an absolute position N, move relative by the distance from here to N.

width

\w'x'
is the width of x in basic units. The idiom for moving by the length of a word is
\h'\w'word'u'

zero motion

\zx
prints x and then doesn't move.