updated Sheets to add an improved spell check option. The spell check option is found under the "tools" drop-down menu. Like the spell check tool in Google Documents and Slides, the Sheets spell check is checked against the web in order to stay updated. Just as you can do in any good spell check tool, you can add your own words and abbreviations to the Sheets spell check dictionary.
Applications for Education
The Sheets spell check isn't going to revolutionize the way that you use spreadsheets, but it could be helpful if your students are submitting quiz answers through Google Forms and you want to quickly check for spelling errors. The spell check may also be helpful to folks who are running scripts in which a misspelled column title could cause the script to fail.