1.
seven o'clock
The time at seven hours past midnight or noon.
Pronunciation
Both しちじ and ななじ are used. しちじ is the standard reading; ななじ is often used to keep しちじ apart from いちじ (一時, one o'clock), for example in announcements and on the phone.
Common patterns
Watch out
7 is read しち or なな depending on the word: 七月 (July) but 七つ (seven things), and 七日 (the 7th day) has a reading of its own.