[EpicEng]

The definition of expatriate (noun) is any person who lives outside their native country. It's a synonym of migrant. An immigrant is "someone from a foreign land", so the only difference appears to be the "settling" part (an expat/migrant has settled somewhere else, an immigrant is simply _from_ another country.)

This is based on the 1.5 minutes I just spent looking these up and is only based on definition (not usage).

[sandworm101]

Migrant suggest some sort of ongoing movement. "Migrant labour" is people who move back and forth chasing work, often inside a single country. An expatriate is someone living in a semi-permanent state outside their home country.

I'd describe someone moving from one part of the US to another on a seasonal basis, someone chasing farm work, as a migrant. I'd call a canadian working for a period of year at a US firm an expatriate. The former is under a continual state of movement that the later is not.