How to Form Past Participles: Rules for Adding "ed" to Verbs

3. Spelling rules for adding ed to form the past participle 
Some regular verbs change their spelling when the ending ed is added to form the past participle.

a. Verbs ending in a silent e
When a regular verb ends in a silent e, only the letter d must be added in order to form the past participle. For example:

Infinitive	Past Participle
to close	closed
to move	moved
to please	pleased
to receive	received

b. Verbs ending in y
When a regular verb ends in y immediately preceded by a consonant, the y is changed to i before the ending ed is added. For example:

Infinitive	Past Participle
to study	studied
to rely	relied
to carry	carried

However, when a regular verb ends in y immediately preceded by a vowel, the y is not changed before the ending ed is added. For example:

Infinitive	Past Participle
to play	played
to convey	conveyed
to enjoy	enjoyed

Exercise 3
Paying attention to the spelling of the past participles, fill in the blanks using the Present Perfect tense of the regular verbs shown in brackets. For example:
      She _________ hard. (to try)
      She has tried hard.

      He ___________ his friend. (to annoy)
      He has annoyed his friend.

c. Verbs ending in a single consonant preceded by a single vowel

The rules concerning the doubling of final consonants which apply when adding the ending ing to form the present participle also apply when adding the ending ed to form the past participle.

Thus, when a one-syllable verb ends in a single consonant other than w, x or y immediately preceded by a single vowel, the final consonant must be doubled before the ending ed is added to form the past participle. In the following examples, the consonants which have been doubled are underlined. For example:

Infinitive	Past Participle
to rub	rubbed
to trim	trimmed
to plan	planned
to stop	stopped

When a verb of more than one syllable ends in a single consonant other than w, x or y immediately preceded by a single vowel, the final consonant is doubled before the ending ed only when the last syllable of the verb is pronounced with the heaviest stress. In the following examples, the syllables pronounced with the heaviest stress are underlined. For example:

Infinitive	Past Participle
to control	controlled
to infer	inferred
to occur	occurred
to permit	permitted
to fasten	fastened
to order	ordered
to focus	focused
to limit	limited

In the first four examples, the last syllable of the verb is pronounced with the heaviest stress, and the final consonant is doubled before ed is added. In the last four examples, the first syllable of the verb is pronounced with the heaviest stress, and the final consonant is not doubled before ed is added.

The final consonants w, x and y are never doubled when the ending ed is added. For example:

Infinitive	Past Participle
to follow	followed
to box	boxed
to portray	portrayed

It should also be noted that final consonants immediately preceded by two vowels are not doubled when the ending ed is added. For example:

Infinitive	Past Participle
to greet	greeted
to rain	rained
to soak	soaked
to treat	treated

Exercise 4
Paying attention to the spelling of the past participles, fill in the blanks using the Present Perfect tense of the regular verbs shown in brackets. For example:
      He __________ the child. (to scare)
      He has scared the child.

      They ____________ the hillside. (to scar)
      They have scarred the hillside.