I am currently studying English language acquisition and an early elementary grade leveled subject's assessment results. The subject was asked to repeat a series of complex sentences. One of the sentences read:
My friend likes to eat ice cream when it's very hot out.
The subject responded:
My friend likes to eat ice cream when it's really hot outside.
I'm curious to know which type of morpholocical word formation would changing the word out to outside fall under? Derivational or compounding?
Also, what about replacing the word very with really even though they both never change their grammatical category? Would this be a simple substitution?
Any input would be appreciated. Thanks