Nelson (1973) - studied the first fifty words produced by eighteen children and grouped them into five categories. classes of objects formed the largest group- it is easier for children to identify things that they can actually touch.
Classes of objects - dog, show, ball, car
Specific objects - mummy, daddy
Actions/events - give, stop, go, up, where
Modifying things - dirty, nice, all gone
Personal/social - hi, bye-bye, yes, no