El Imperativo endings confusion

Question

Is there some consistency I am missing in endings in -ar, -er, and -ir verbs in el imperativo? Ex's: Levántate (-ar), siéntese (-ir), córtense (-ar), levantémonos (-ar), acuéstate (ar). Something to do with reflexive?

Accepted Answer

Hola MB
The imperative needs to be seen not as a whole conjugation because depending on who the imperative is directed to, the ending will vary. Being reflexive or not won't change the ending. For example, for levantarse:

Tú, levántate
Vosotros, levantaos
Usted, levántese
Ustedes levántense
Nosotros levantémonos

This is the reason why in Kwiziq the lessons related to the affirmative imperative are divided into different subjects. 
Here are our lessons on affirmative imperative. Have a look at the links with the lessons at the bottom, you need those that say "Forming the imperative of/for..." 
Saludos
Inma