I shall endeavour to provide a humble explanation for that. Generally speaking, language syntax in gretl consists of three groups: commands, functions and “the rest”. Since it is an econometrics software package, it deals with statistic datasets. If you tell it a command, it does something: “*info*” describes a dataset in the output window, “*ols* y x” estimates a model, “*omit* const” conducts a test whether the intercept (constant term) can be treated as zero and omitted etc. If you use a function, well, a function grabs something as input and yields something as output. Most of the functions are mathematical and statistical. Example: *genr* r = *round*(x) --- *genr* is a command, it does something, whereas *round*(arg) is a function that returns a rounded-to-zero value of its argument. Another example: after a regression is estimated, the command *vif* calculates variance inflation factors and produces a table with a bunch of numbers, whereas *$rsq* is a function: it is equal to the R-squared coefficient from the last estimated model. A bare function is senseless: one cannot simply write *exp*(x) and enjoy the fruits. A function is an instrument that is used in commands; a command is a script that uses functions. The *ols* command uses functions of matrix multiplication, assigns some values to the functions related to the regression estimation and produces a table. That’s the basic difference. Please correct me if I wasn’t precise at all. Yours sincerely, Andreï V. Kostyrka -- С уважением, —Андрей Викторович Костырка.— http://kostyrka.ru, http://kostyrka.ru/blog 2014-04-08 0:25 GMT+04:00 Logan Kelly <logan.kelly(a)uwrf.edu&gt;: