swim的过去式是：swam
swim的过去完成式: swum; swim的现在进行式: swiming
⒈过去发生的而已经结束的动作需要用一般过去式来表示。
⒉表示过去某个时间里发生的动作或状态。
【过去时态】表示行为、动作和状态在各种时间条件下的动词形式。
【过去时态结构】是指过去时态下的动词形式的语法构成。
规则动词
一般动词直接加-ed；e.g.look-looked
以e结尾的动词直接加-d，e.g.dance-danced
辅音字母加y结尾的，改y为i加ed，e.g.study-studied
以重读闭音节结尾，末尾只有一个辅音字母，双写这个辅音字母加-ed、e.g.skip-skipped
﹝英语26个字母中，除了a，e，i，o，u ‹即aoeiu› 这几个元音字母外，其他都是辅音字母）
动词过去式与原形相同
动词过去式以ought或aught结尾
动词过去式由原形结尾的end变为ent
动词过去式以elt，eft，ept结尾
动词过去式与原形比较，其中一个元音字母发生改变
动词过去式以ew结尾
动词过去式ee变为e
情态动词
is-was
are-were
am-was
go-went
do,does-did
bring-brought
make-made
have-had
run-ran
tell-told
eat-ate
get-got
draw-drew
put -put
read-read
take- took
die-died
see-saw
fly flew
cut cut
make made
meet met
tell told
build built
lend lent
lose lost
hear heard
buy bought
see saw
choose chose
forget forgot
sink sank
sing sang
begin began
swim swam
ring rang
drink drank
fly flew
draw drew
lie lay
wear wore
know knew
teach-taught
swim-swam
stand-stood
keep-kept
fight-fought
think-thought
规则情态动词：
call- called
live- lived
learn- learned/learnt
walk,talk +ed
jump +ed
use+d
plant,want,water,play +ed
stop- stopped
study- studied
visit- visited
其他变化
1．原形-过去式-过去分词全相同
cost---cost---cost 价值
cut --- cut --- cut 切，割，砍
hit --- hit --- hit 打
hurt---hurt---hurt 伤害
read---read---read 读
put --- put ---put 放
let --- let --- let 让
shut---shut---shut 关
2. 过去分词与原形相同,过去式改o/u为a
become---became---become 变得，成为
come---came---come 来
run --- ran --- run 跑
3. 原形-过去式-过去分词是i-a-u的变化
begin---began---begun 开始
drink---drank---drunk 喝
ring---rang---rung 打电话
sing---sang---sung 唱（歌）
swim---swam---swum 游泳
4. 过去分词在原形后加-en
eat ---ate---eaten 吃
fall---fell ---fallen 落下；跌倒
5. 过去式和过去分词都去掉原形的一个e
feed---fed ---fed 喂养，饲养
meet---met---met 碰到，见面，会面
6. 过去分词在原形后加-n
blow--- blew--- blown 吹
grow---grew---grown 种植；生长
throw---threw---thrown 投；掷；扔
know---knew---known 知道；懂得；认为
draw --- drew --- drawn 画
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