morpheme
Comparemonomorphemic
The words were marked for whether they were monomorphemic or bimorphemic (e. g. "sock" vs. "boys").
Bimorphemic clusters include past forms such as "missed".
SMART Vocabulary: related words and phrases
Linguistics: morphology & parts of words
-athon
affix
affixation
agglutinate
agglutinative
analytic
contraction
ion
ism
libfix
monomorphemic
monosyllabic
morpheme
morphological
suffix
syllabify
synthetic
that'd
that'll
that's