不规则动词
1.A-A-A型（无变化的动词）
cut-cut-cut let-let-let hit-hit-hit put-put-put cost-cost-cost hurt-hurt-hurt read/rid/-read[red]-read[red]
2.A-A-B型（现在式和过去式同形）
beat-beat-beaten
3.A-B-A型（现在式和过去分词同形）
come-came-come
become-became-become
run-ran-run
4.A-B-B型（动词的过去式与过去分词相同）
（1）词尾的“d”变为“t”或词尾是“n”加“t”
build-built-built lend-lent-lent send-sent-sent spend-spent-spent
burn-burnt/burned-burnt/burned learn-learnt/learned-learnt/learned
mean-meant-meant
（2）把原形变为aught及ought的变化（如果原形有a则是aught，无a则是ought）
buy-bought-bought bring-brought-brought think-thought-thought
fight-fought-fought catch-caught-caught teach-taught-taught
（3）eep变ept或过去式、过去分词含有/e/音的动词
keep-kept-kept sleep-slept-slept sweep-swept-swept leave-left-left
