還是有區(qū)別的,second language是第二語言,foreign language是外語（非母語）.一個(gè)人的foreign language可以有好幾種,second language只有一個(gè)
every language used by a foreign nation which is different from your native language can be called a foreign language.
however,the notion of a "second language" can be explained like this:
this is a language u also have a good command of.in offical or common accasions,u may use your first language as first prioriry usually,but when first language can't be used to communicate with each other,the second language is up to.