分钟

Use it whenever you're measuring how long something takes: 五分钟 'five minutes,' 等一分钟 'wait a minute.' The key difference from English: when you tell the clock time, Chinese drops 钟 and just uses 分 — '3:15' is 三点十五分, never 三点十五分钟. So 分 alone names a clock minute; 分钟 names a span of minutes.

Also note that 分钟 is itself a noun acting like a unit, so you never need an extra measure word: say 五分钟, not 五个分钟. The character 钟 (originally 'bell / clock') is also the second character in 钟表 'clock' and 时钟 'wall clock.'