counter for ships (large boats); counter for half of a pair (e.g. half of a folding screen); counter for fish, birds, arrows, etc.
one eye; eye (for pictures, etc.)
one-armed person; one-handed person
a glimpse of an object's outlines
sharp eye; critical eye; discerning eye; an opinion
every single word and phrase; each and every word
the sound of one hand clapping (a classic Zen koan)