What is a purpose clause and how can they be identified and translated?

PURPOSE CLAUSES
Purpose clause: These express the aim or purpose of the action of the main clauseFor example in English, Marcus went to the shop to buy eggs is a purpose clause as the purpose and reason for the main clause (going to the shops) is explained.PCs are introduced by 'ut' (so that, in order that) or, if negative, 'ne' (so that not, lest) PCs take the subjunctive (=the second verb, after the ut/ne will be in the subjunctive mood) E.g. Marcus ad tabernam fuit ut ova emeret
IdentificationSimply: through seeing ut/ne + subjunctive N.B. IMPORTANT RULEWhen the main clause is in the present or future tense, the subordinate clause (the clause after the ut/ne) will be in the PRESENT subjunctive.When the main clause is in the imperfect, pluperfect or perfect tense, the subordinate clause (the clause after the ut/ne) will be in the IMPERFECT subjunctive.This rule is key when composing from English into Latin, something that is now tested at GCSE.

TranslationWhen you identify a purpose clause, the literal translation of ut = so that, in order that and ne = so that not However ut is better translated as an English infinitiveE.g. Marcus ad urbem festinavit ut amicos videret = Marcus hurried to the city to see his friendsOR literally; Marcus hurried to the city so that he might see his friends (N.B. Note the perfect tense, therefore the imperfect subjunctive. Understanding this is key to composing a PC)
And ne is better translated as 'to avoid + a participle'E.g. ex urbe abierunt ne Marcum viderent = They departed from the city to avoid seeing Marcus OR literally; They departed from the city so that they might not see Marcus