split hairs

(verb) to be very exact and specific about something

Example Sentences:

When I got my wife a Diet Coke, she got mad at me because she wanted a Coke Zero. I told her not to split hairs.

Student: Can I go to the bathroom?
Teacher: May I go to the bathroom, you mean?
Student: You are splitting hairs.

From the Blogs:

Spinning and splitting-hairs

Media:

Similar idioms:

1. let it slide
2. hit the nail on the head
3. see through someone
4. prick up one’s ears