Code-switching: the grammar of switching languages mid-sentence.
Multilinguals switch following consistent grammar rules. Not random, not broken, not laziness.
Spanglish (US): "Dame el remote control, por favor."
Taglish (PH): "Nag-shopping ako kahapon."
Hinglish (IN): "Yaar, this traffic is so bad, let's take the metro."
Switches cluster at grammatical boundaries. Poplack (1980) showed speakers keep both grammars running at once.
