Hi Jonathan, "Preocuparse" is a reflexive verb. "Preocupar" mean to worry or bother. "Se" refers to yourself or oneself. When you PREOCUPAR...SE, you are worrying yourself or preoccupy yourself about something. If you use the tú form, then you worry yourself as TE. If I am worrying, then I am preoccupying myself "ME" with something. Thus: ME preocupo - I preoccupy MYSELF TE preocupas - you preoccupy YOURSELF SE preocupa - he preoccupies HIMSELF NOS preocupamos - we preoccupy OURSELVES OS preocupáis - You all preoccupy YOURSELVES SE preocupan - They preoccupy THEMSELVES I hope this answers your question.

The reason it's "no te preocupes" is because affirmative "tú" commands are different from negative ones - for the most part, affirmative ones are the third person singular of the present indicative tense. However, for negative ones it's conjugated as the subjunctive tense - "preocupes". So, no, you can't say "no te preocupa" because it's not an affirmative command.

(tú) no te preocupes (usted) no se preocupe

To expand on what Sam said: Spanish really only has an *affermative* imperative in the *second* person (singular or plural), and that even has some special forms you have to memorize (e.g. haz, ven). In all other cases you use the corresponding subjunctive – not only for negative imperatives, but also for 1st or 3rd person.

this is a proble with the conjugation remember the third person is used for the polite form usted the second one is tu always finish in s and it is not a time it is a mood you gonna see that there is a reltion between the subjunctive and the imperative just try to find patterns to make easier