The sign for "so" is basically a gesture meaning "Well?
What?" The facial expression is used to turn it into a question by
raising your eyebrows (as in "What's your point?) or a rhetorical
question. If you don't raise your eyebrows it can mean such things
as, "So, then I ...."
"SO?" "Well?" "What is your
point?" "What do you want from me?"


Notes:
* If I wanted to sign, "I'm going to school so I can get a
better job." I could instead sign: "I go school WHY?
Better job" or "I go school for better job." Or I could
sign "FOR-FOR?" which equals "What for?"
* There is another sign for "SO" that is used "out
there" in the real world. If is different from the one I show here.
It uses two "S" hands, the dominant hand makes a downward / forward
movement and glances against the side of the left hand --
but that sign is "English" and not "ASL" based. I'm
not going to do a graphic for it since too many of my students will
latch onto it and start misusing it. Stick with the gesture
above and your signing will look more like that which is done by
native Deaf adults.
Also see: "SO-SO."
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American
Sign
Language (ASL) online at American Sign Language University ™
ASL resources by Lifeprint.com © Dr. William Vicars