There aren’t many verbs where the basic form, past tense and past participle forms are all the same. I can think of one or two verbs that end with -t that do not change. Cut and let would be two examples. Consider the following:
'I let Roger drive the car whenever he wants to.'
'I let Roger drive because I wasn’t feeling very well.'
'If you hadn’t let him use your credit card, you wouldn’t now be overdrawn.'
'I always cut my toenails with a hacksaw!'
'I cut my finger when I tried to use my father’s saw.'
'I’ve cut my finger and it hurts!'
Check in your grammar books or dictionaries and see if you can find some more examples of verbs that do not change.
For the rest, verbs are either regular and formed in the past tense and past participle with an ‘-ed’ ending, or they are irregular, like ‘build’ in your example, Carmen, which becomes ‘built’ in both past tense and past participle forms. Many irregular verbs have different forms for past tense and past participle. Consider the following:
Irregular verbs
basic form
past tense form
past participle form
be
was/were
been
begin
began
begun
blow
blew
blown
choose
chose
chosen
come
came
come
As you can see from the beginning of this alphabetical list, many common verbs in English are irregular and I am afraid it is a matter of learning what is correct in each case as there is no clear pattern to follow.
Here are eight more common irregular verbs. Test your knowledge to see if you can get them all right.
Note that for regular verbs where the past ending is always written -ed there are three distinct pronunciations in English.
The past tense -ed ending is sometimes pronounced /t/, sometimes /d/ and sometimes /id/. Which we use depends on which letters the verb ends with in the basic form. If the basic form ends with /d/ for instance, as in fold, it is pronounced /id/ in the past tense and past participle form.
Say it to yourself and listen to how you say folded. If it ends with /p/ in the basic form, as in clap, then it is pronounced /t/ in past endings. Say it to yourself and listen to how you say clapped.
Now try the following exercise. (It is a technique that I learnt as a dictation exercise from Mario Rinvolucri and Paul Davis.) The first three examples have been done for you.
