droop, suspend, hang, slouch
垂 centers on something hanging down loosely: drooping, suspending, or slouching. The idea of letting something hang extends naturally to causing something to hang (suspend) or adopting a drooping posture.
垂 is thought to depict something hanging down, possibly a plant or branch drooping. The modern form retains a vertical line with crossing strokes suggesting suspension.
The vertical stroke with crossing lines looks like a cord with something dangling from it. Picture a heavy fruit pulling a branch downward: 垂 is drooping and hanging.
For スイ, imagine a swing hanging from a tree branch, swaying gently: swing -> スイ, and the seat droops under weight.
sauce (esp. soy or mirin-based dipping sauce)
vertical
to dribble; to spill
incontinence; soiling oneself; wetting one's pants
kanji "cliff" radical (radical 27)
waterfall
to hang; to droop; to dangle; to sag; to lower; to pull down
pull-up (exercise); chin-up; chinning
drooping; hanging down
tip-off (to the authorities); information (on); anonymous report
hanging banner; hanging screen; curtain
weeping form (e.g. tree)
avid desire; craving; thirst; envy
appendicitis
to hang one's head; to droop one's head
to hang; to dangle
(vermiform) appendix
pituitary gland; pituitary body; hypophysis
dying by the roadside; dying a dog's death
rafter