particular
"Particular" is a very useful word in English with a handful of related but distinct meanings. It works as both an adjective and a noun, and you will encounter it constantly in everyday conversation, writing, and formal contexts. Here are the most important senses to know.
When you describe a person as 'particular', it means they have very high or precise standards and are not easily satisfied. They care a lot about things being done in exactly the right way. It is similar to saying someone is 'picky' or 'choosy', but 'particular' sounds more neutral and polite.
everyday language · Modern, widely used
As a noun, 'particular' (almost always used in the plural: 'particulars') refers to the specific facts or details about something. You will often see this in formal or official contexts, like when someone asks for your personal information.
formal / official language · Formal, still widely used in official contexts