FYI is an abbreviation that stands for "for your information". It is commonly used in both personal and business correspondence to show that information is simply being shared and that no immediate action is required or expected. FYI was first written in 1941 in an office memo and has been widely adopted since then. It is often used in email, text messaging, and instant messaging. In formal situations, it is a good idea to write FYI in all caps to look more professional. FYI can come across as condescending or abrupt, so its important to be aware of the tone of your message when using this acronym. If youre unsure whether FYI is appropriate, you can always err on the side of caution and simply write out the phrase "for your information" in full.