Conjugation is the process of inflecting a verb by adding affixes or changing certain letters in the base verb form to give the verb a different syntactic function. The base verb or lemma form of a verb is called the infinitive.

Most verbs in English can be conjugated as follows. Use the infinitive for most forms, except add "ed" for the past and past participle, add "ing" for the present participle, and add "s" for the third person singular. A few simple modifications are needed for the following cases.

1. When the infinitive ends in "e", add "d" for the past and past participle, and replace the final "e" with "ing" for the present participle.
2. When the infinitive ends in ch, s, sh, x, or z , add "es" to create the third person present.
3. When the infinitive ends in a consonant preceded by a short vowel (e.g., "chop"), double the final consonant and add "ed" to the infinitive form to create the past and past participle, double the final consonant and add "ing" to create the present participle, and add "s" to create the third person present.
4. When the infinitive ends in "y", replace the final "y" with "ied" to create the past and past participle, add "ing" to create the present participle, and replace the final "y" with "ies" to create the third person present.

There are American/British differences as regards consonant doubling. MorphAdorner maintains a list of verbs whose final consonant is typically doubled in British English, and always doubles the consonant for verbs on that list. Optionally, MorphAdorner knows how to generate the American spelling without the doubled terminal consonant for many common forms.

Verbs whose conjugations follow the rules above are called regular verbs. Verbs which do not follow these rules are called irregular verbs. English has several hundred irregular verbs, which include some of the most commonly used. MorphAdorner checks a list of irregular verb forms before applying the regular conjugation rules above. There are a few ambiguities since some common verbs take different forms depending upon their meaning. Examples include:

Some verbs can take either regular or irregular past or past participle forms (examples: shine, kneel, light, prove, wake). MorphAdorner usually generates the regular form unless the irregular form appears to be more commonly used.

You can try MorphAdorner's English verb conjugator online.