A term here is a predictor from a linear model (e.g. "weight" or "weight:height") whereas a variable is a column in a data frame (e.g. "weight" or "height").
df_term(term, data)df_variable(variable, data)
The term or variable to get the degrees of freedom for. It should match one
of the column names in data, or, if it is an interactive term (e.g. "weight:height"), all
components must be column names in data.
The data the term is from.
The degrees of freedom used by the term or variable in the model (as an integer).