1) interchangeable in some way. 2) when you are reading time, 分 is more common. -现在是什么时间？--现在五点零三分。(what time is it now? It's 5:03). By the way, sometimes we even omit 分 when describing certain times. 五点一刻，五点二十，五点半 （5:15, 5:20, 5:30) 3) when you are describing a duration of time, 分钟is used. --你等多久了？ --才等五分钟。 (-how long you've been waiting? --Just 5 minutes.) 4) to avoid confusion; sometimes they carry completely different meanings. let's say you are describing something is so deeply [adjective], to a certain degree. one example being: He works so hard that he won't even waste a minute. 他如此努力，以至于一分钟都不肯浪费。 another example: he won't make even the slightest concession. 他一分一毫都不肯让步。in this example, 分 doesn't mean literal "ˈminit", but "mīˈn(y)o͞ot".

分: minute，point，mark，divide…（can be n.&v.） 分钟:minute(n.)

if someone ask you what's the time? you can see X点XX分。like 8点30分 if someone ask you how long will it take? you can see XX分钟。like 20分钟

分钟 a noun, which means minutes. 分 can be a noun or verb depending on the context. 分 noun mostly means the grade or point you get in an exam or sport. For example, 他得了几分呀？ can also mean the minimum currency unit in Chinese Yuan. For example, 一角等于十分，十角等于一元。 分 verb, mostly means to break up with someone. For example, 他们分了吗？他们分了呀。 can also mean to divide something into several parts for a group of people.,For example, 咱们几个把任务分了。