Before revision:  One particularly challenging phenomenon is the use of multiple languages within one utterance, also called Code-Switching (CS) . Whereas monolingual social media data already provides many problems for natural language processing, CS adds another challenging dimension. One solution that is commonly used to improve processing of social mediadata is to translate input texts to standard language first. This normalization has shown to improve performance of many natural language processing tasks.
After revision:  One particularly challenging phenomenon is the use of multiple languages within one utterance, also called Code-Switching (CS) , is frequently overlooked by these normalization systems, despite its common use in social media.