When phenotypic characters are described in the literature, they may be constrained or clariﬁed with additional information such as the location or degree of expression, these terms are called “modiﬁers”. With eﬀort underway to convert narrative character descriptions to computable data, ontologies for such modiﬁers are needed. Such ontologies can also be used to guide term usage in future publications. Spatial and method modiﬁers are the subjects of ontologies that already have been developed or are under development. In this work, frequency (e.g., rarely, usually), certainty (e.g., probably, deﬁnitely), degree (e.g., slightly, extremely), and coverage modiﬁers (e.g., sparsely, entirely) are collected, reviewed, and used to create two modiﬁer ontologies with diﬀerent design considerations.