below, down, descend, give, low, inferior
下 centers on a lower position or downward direction: being below, moving down, or descending. The senses of giving and inferiority are natural extensions of lowering something or being lower in status.
to give; to confer; to bestow
under (guidance, supervision, rules, the law, etc.)
below; down; under; younger (e.g. daughter)
not exceeding ...; not more than ...; ... and under; ... and below; ... or fewer
low rank; lower position; subordinate position; lower order (e.g. byte)
underground; below the ground
to come down; to go down; to fall; to drop; to sink; to get lower
unskillful; poor; awkward
humble position; inferior
fall; decline; lowering; deterioration; degradation
subordinate person
underwear; undergarment; underclothes; lingerie
top and bottom; up and down; high and low; above and below; upper and lower ends
top and bottom; high and low; above and below; upper and lower ends; up and down
the following
subway; metro; underground (railway)
down-train; train heading toward the ending point of its route
to make a decision; to draw a conclusion
the whole world
throwing down; dropping; airdrop
fall; drop; descent; coming down
lower half of the body; nether parts
socks; sock; stockings; stocking
trivial; trifling; insignificant; not worth bothering with; worthless; useless; good-for-nothing
下 is a simple ideograph: a horizontal line with a vertical stroke and a short diagonal mark below it, indicating the concept of 'below' or 'down' relative to a reference line.
The horizontal line is a reference point, and the vertical stroke with the small diagonal mark points downward. Think of an arrow pointing below a surface: 下 means below or down.
For カ, imagine a car going down a steep hill: car -> カ, and the car descends lower and lower.