间 / 期间【jiān / qījiān】

间 on its own is a shortened, written 之间. It joins straight onto a one- or two-syllable noun and means "between" or "among" the members of it.

期间 – during

期间 goes after an event or a period and means "during it". It is the usual written word for "during", in notices, news and formal letters.

In a chat, the same idea is …的时候.

Fixed time words

间 also sits inside a set of time words that act as single words: 课间 (the break between classes), 晚间 (evening), 夜间 (night-time), 瞬间 (an instant), and 年间 after a reign or era name.

When 间 is not enough

Bare 间 needs a short noun right in front of it. After a pair joined by 和, or after a longer phrase, it takes the full 之间.

• × 我和他间 → 我和他之间

The other 间, a measure word for rooms (一间教室), is the same character and the same reading but a different word.