The past tense and past participle of the verbs learn, spoil, spell (only in the word-related sense), burn, dream, smell, spill, leap, and others, can be either irregular (learnt, spoilt, etc.) or regular (learned, spoiled, etc.). In BrE, the irregular and regular forms are current; in some cases (smelt, leapt) there is a strong tendency towards the irregular forms (especially by speakers using Received Pronunciation); in other cases (dreamed, leaned, learned) the regular forms are somewhat more common. In AmE, the irregular forms are never or rarely used (except for burnt and leapt).
Nonetheless, as with other usages considered nowadays to be typically British, the t endings are often found in older American texts. However, usage may vary when the past participles are actually adjectives, as in burnt toast. (Note that the two-syllable form learnèd /'lɜːnɪd/, usually written simply as learned, is still used as an adjective to mean "educated", or to refer to academic institutions, in both BrE and AmE.) Finally, the past tense and past participle of dwell and kneel are more commonly dwelt and knelt on both sides of the Atlantic, although dwelled and kneeled are widely used in the US (but not in the UK).
