a fitted model object, typically. Sometimes also a summary() object of such a fitted model.

character specifying for which component of the model coefficients should be extracted.

for the aov, lm, glm, mlm, and where applicable summary.lm etc methods: logical indicating if the full variance-covariance matrix should be returned also in case of an over-determined system where some coefficients are undefined and coef(.) contains NAs correspondingly. When complete = TRUE, vcov() is compatible with coef() also in this singular case.

additional arguments for method functions. For the glm method this can be used to pass a dispersion parameter.