'Sis' is much more informal than 'sister', so you would not use 'Sis' in referring to her to others outside the family, in making introductions, in writing, at work, at formal events such as weddings or funerals.
Depending on the standards of your family, it may also not be acceptable at family dinners or anywhere in public. Also, regardless of the occasion, it is only OK if your sister does not mind being called Sis.
bro, sis
Unless her name is Eve or Hannah, you might want to stick with Sis.
The abbreviation for sister is "Sis."
if you have a sister whose first name starts with g she is considered a g sis or if you are a sister and your first name starts with a g you are considered a g sis
I have no sister. I'm the one and only daughter of my parents.
Bio-Sis is when you're sis or sister is taking a bio or biography class. Hope this was helpful =)
"Sisko" (sis - ko) = sister
sis
yes a sis
Sis
Yes.. He has one sis.
Sister has two syllables. The syllables are sis-ter.