Objects of prohibeo

[Leizorex]

Contemplating the word, "prohibeo", it seems to take two objects, sometimes.

I prohibit eating in school...Prohibeo edendum in schola.

I prohibit you from eating....Prohibeo te ......?

Similar question, if I say, "thanks you for the help" (which I do), do I say, Do gratias tibi auxilio?

 

[Pacifica]

I prohibit eating in school...Prohibeo edendum in schola.

Edendum is wrong there. Perhaps you should review the use of gerunds and gerundives. You could read section 1. of this post, for instance, though you can probably find basic explanations in any grammar.

You need an infinitive, most likely passive impersonal since the subject of the eating is not expressed: prohibeo edi in schola.

If you don't know what "passive impersonal" means you can find an explanation here (section 5) for instance.

I prohibit you from eating....Prohibeo te ......?

... edere.

Similar question, if I say, "thanks you for the help" (which I do), do I say, Do gratias tibi auxilio?

Not quite. One usually says gratias ago rather than do, and "for the help" should be pro auxilio or de auxilio.

 

[Leizorex]

Gratias magnas ago pro auxilio pretioso!

 

[Quasus]

When in doubt about the usage of particular word, you can consult Forcellini: http://lexica.linguax.com/forc2.php?searchedLG=prohibeo The entries are very structured and possible constructions are listed, as here:
a) Cum Accusativo personae et Ablativo rei cum praep. ab.
b) Cum Accusativo personae aut rei, et Ablativo rei sine praeposit.
c) Cum Accusativo tantum rei aut personae.
d) Raro admodum cum Dativo, aut cum Genitivo, aut cum Ablativo et praepos. de
e) Absolute.
f) Cum particulis ut, ne, quin, quominus.
g) Cum infinito.
Here "absolute" means "without any dependent words" and "cum infinito" includes AcI. As for ut/ne/quin, you should consult the grammar. Thus, in your case it would be either te edere prohibeo or prohibeo ut edas.

But those probably don't mean what you want them to. The same Forcellini explains the meaning: "Prohibeo est idem ac procul teneo, arceo, submoveo, impedio, ne quid fiat: quasi porro habeo, κωλύω, εἴργω (It. tener lontano, impedire; Fr. empêcher, retenir, détourner; Hisp. impedir, detener, desviar, estorvar; Germ. zurück-, entfernt-, abhalten, verhindern, abwenden; Angl. to Keep off or away, keep or ward off, debar, hinder, impede, stop, prevent, prohibit)", so essentially it's said of an obstacle or an impediment. Even though it can be close to "prohibit": "2. Speciatim est vetare, interdicere, proibire, vietare. Distant tamen veto, et prohibeo, quod vetamus dictis, prohibemus etiam factis", you may prefer veto.