[2] In the English language, inflectional affixes include third person -s, verbal -ed and -ing, plural -s, possessive -s, comparative -er and superlative -est.
[4] Nagy et al. (1993) summarizes how knowledge of the meanings of common English suffixes underwent significant development between fourth grade and high school.
[6] There have also been studies on non-native English speakers and learners on their knowledge and understanding of word families.
[7] In addition, a study of Japanese students learning English showed poor knowledge of the affixes studied, showing a division between their knowledge of a word's meaning and a derivative form of a separate word (e.g. stimulate versus similar, disclose and far).
[8] To conclude their study, Schmitt and Zimmerman have provided the following for those teaching word families as a guideline:[7]