Sioux and sous are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It’s suggesting what word you may want to save time, but quite often, its suggestions are pretty off base. They don’t help you out, but they do make you laugh.
Sioux is a proper noun. It is a French Canadian word for a tribal nation in North America. Sioux tribes are associated with territories in the upper Midwest and Plains states, and two provinces in southwestern Canada.
Sous is an adjective. It’s a French word used with “chef.” In a professional kitchen, the Sous chef ranks just below head chef. They are responsible for the quality of food leaving the kitchen including its sources and its presentation.
The following sentence uses both words correctly:
Snana was making plans to launch a food truck that blended Sioux food traditions with international dishes. With the proceeds, she wanted to attend culinary school and quickly rise to a sous chef position in Billings. Her ultimate goal was owning her own restaurant.