The United Nations Convention on the Protection of the Rights of All Migrant Workers and Members of Their Families defines migrant worker as follows: The term migrant worker refers to a person who is engaged or has been engaged in a remunerated activity in a State of which he or she is not a national.
A mathematical expression can be as simple as 2 + 4 or as complex as -4xy + 8 x - 5(x/y). All mathematical expressions contain terms and each term has a coefficient, the numerical factor.
An expression is basically an incomplete mathematical sentence. It is like any normal phrase in the English language. Compared to expressions, equations are more complete. They are homologous to what completely structured English sentences are.