A clause with ut ("so that"), ne ("so that … not") or quo and the subjunctive says what an action is for.
Recognise: ut, ne, ut ne (= ne) or quo + subjunctive, after a main clause that is complete in itself. There is no signal word such as ita or tam in the main clause; that would make it a result clause.
Translate "so that … may", "in order to", or a plain "to": quo boni aliquid addiscas "so that you may learn something good". ne is "so that … not", "lest": ut ne murmurans moriaris "so that you do not die grumbling".
quo is used mainly with a comparative ("so that the more …"); Gataker also uses it alone for "so that". After a present or future main verb the subjunctive is present; after a past one it is imperfect (ne incideret).
Purpose is also expressed by ad + gerund or gerundive (ad animum serenandum "to calm the mind"), by qui + subjunctive ("to, in order that he"), and by a genitive gerund or gerundive with causa (vivendi causa "in order to live").