They pronounce words differently, they use different vocabulary words and they use different grammatical forms. I've witnessed this co-exist with my friends who are Russian. I"m always there correcting them on their English and find it hard for them to use terms correctly. Phonology is the science of speech sounds. I've heard grown people with a complete range of vocabulary usage continue to pronounce words the way they think sounds right to them. Lexicons refer to vocabulary and word meaning. Syntax means learning between dialects may cause differences in beginning reading. Perception is in terms of auditory and visual discrimination. Affective domain is before any approach is applied to teach reading to the dialectically different child it's important to understand that the individual language is his most important possession. This set of expectations is the most wasteful and destructive phase of the present education system. It reduces aspirations of both students and teachers. Most students can master what schools have to teach. Schools basic task is to determine is what needs to be mastered. Kids come from other countries into America only knowing there background language. I was mixed in with some of these kids in many classes. Some might be learning English and some are completely oblivious to the new language. But the adaptation process will take place, some might pick up quick and some might struggle for some years until you could say they know English. It all has to do with there environment and there interactions that creates practice for them besides schooling.
A virtually complete grammar will have been developed by age four or four and a half. This is true over a wide range of intelligence and environments. The learning takes place with little or no instructions. Language is a productive system. Formation of yes and no questions illustrates another kind of rule of transformation.