From Yahoo Answers: "LEARN is the present tense, and the conjugated form of the verb "to learn".
It can be converted to the past tense in the following ways:
I LEARNED lots of things along the way. The main verb is "learned".
LEARNT is the "past participle" in the following sentences. (Past participles are used in conjunction with other verbs).
I have learnt not to be prejudiced towards Americans or people of other nationalities. (creziauk!)
I had learnt my lesson on peer pressure, the hard way."