Interlingual vs. Intralingual
There are two types of interferences with second language aquisition.
Interlingual is the effect of language forms when two languages cross or overlap. It involves with accurate pronunciation or proper way of describing something. For example, instead of "Jackbook" someone may say "the book of Jack."
I speak Enlgish more than my native tongue and I find myself constantly doing that when I try to translate something in English to Hmong. In English the adjective goes before the noun and in Hmong it is the opposite. In Hmong to say "the blue sofa" is to be said "the sofa that is blue", however, I usually end up saying it the English way and my parents will give me a wierd look!
Intralingual has more to do with proper usage of grammer. Intralingual usually occurs once a large portion of the second language has been acquired. This is where they start making mistakes of the English language that is not explicitly taught, such as, irregular verbs and the correct or incorrect usage of articles.