"ov": observed variables
"ov.x": (pure) exogenous observed variables (no mediators)
"ov.nox": non-exogenous observed variables
"ov.model": modeled observed variables (joint vs conditional)
"ov.y": (pure) endogenous variables (dependent only) (no mediators)
"ov.num": numeric observed variables
"ov.ord": ordinal observed variables
"ov.ind": observed indicators of latent variables
"ov.orphan": isolated observed variables (only their intercepts or variances appear in the model syntax)
"ov.interaction": interaction terms (defined by the colon operator)
"th": threshold names (ordinal variables only)
"th.mean": threshold names (ordinal and numeric variables, if any)
"lv": latent variables
"lv.regular": measured latent variables (defined by =~ only)
"lv.composite": composites (defined by <~ only)
"lv.x": (pure) exogenous variables
"lv.y": (pure) endogenous variables
"lv.nox": non-exogenous latent variables
"lv.nonnormal": latent variables with non-normal indicators
"lv.interaction": interaction terms at the latent level
"eqs.y": variables that appear as dependent variables in a
regression formula (but not indicators of latent
variables)
"eqs.x": variables that appear as independent variables in
a regression formula